<PAGE>   1
                                                                   EXHIBIT 10.21

                          REGISTRATION RIGHTS AGREEMENT

               This REGISTRATION RIGHTS AGREEMENT (this "Agreement") is made and
entered into, as of July 1, 2001 and effective as of the date of the closing of
the Initial Public Offering (the "Effective Date"), by and between The Advisory
Board Company (the "Company") and David G. Bradley ("Bradley"), Jeffrey D.
Zients and Michael D'Amato (Bradley, Mr. Zients and Mr. D'Amato collectively,
the "Stockholders").

               WHEREAS, the Stockholders will own all of the outstanding shares
of the Company's capital stock as of the date of the Initial Public Offering;
and

               WHEREAS, in order to induce Bradley to consent to the Initial
Public Offering, the Company desires to enter into this Agreement to provide the
registration rights set forth in this Agreement.

               NOW, THEREFORE, in consideration of the recitals above and the
agreements and covenants contained in this Agreement, the Company and the
Stockholders agree as follows:

               1.     Definitions. As used in this Agreement, the following
capitalized terms shall have the following meanings:

                      (a)    The term "1933 Act" means the Securities Act of
1933, as amended;

                      (b)    The term "1934 Act" means the Securities Exchange
Act of 1934, as amended;

                      (c)    the term "Common Stock" means shares of common
stock, par value $.01 per share, of the Company;

                      (d)    the term "Holder" means the Stockholders and any
other person holding Registrable Securities to whom the registration rights
under this Agreement have been transferred in accordance with Section 10 hereof;

                      (e)    the term "Initial Public Offering" means the public
offering pursuant to the first registration covering any capital stock of the
Company;

                      (f)    the term "Lock-Up Agreements" means the lock-up
agreements entered into by the Company and the Stockholders with the
underwriters managing the Initial Public Offering in connection with the Initial
Public Offering;

                      (g)    the term "Misstatement" means an untrue statement
of a material fact or an omission to state a material fact required to be stated
in a registration statement or prospectus or necessary to make the statements in
a registration statement, prospectus or preliminary prospectus not misleading;
<PAGE>   2

                      (h)    the terms "register," "registered," and
"registration" refer to a registration effected by preparing and filing with the
SEC a registration statement in compliance with the 1933 Act and the declaration
or ordering by the SEC of effectiveness of such registration statement;

                      (i)    the term "Registrable Securities" refers to (i) any
and all of the shares of Common Stock held by the Stockholders as of the
Effective Date, and (ii) any and all securities of the Company issued as a
dividend or other distribution with respect to, or in exchange or replacement of
any such shares, except that any such Common Stock or securities shall cease to
be Registrable Securities when and to the extent (i) a registration statement
with respect to the sale of such Common Stock has become effective under the
1933 Act and such Common Stock has been disposed of in accordance with such
registration statement; (ii) such Common Stock has been sold to the public
pursuant to Rule 144 or any successor provision under the 1933 Act; (iii) such
Common Stock shall have been otherwise transferred, new certificates therefor
not bearing a legend restricting further transfer shall have been delivered by
the Company and subsequent disposition of such Common Stock does not require
registration or qualification under the 1933 Act or any similar state law then
in force in the opinion of legal counsel for the Company and the Stockholders;
or (iv) such Common Stock shall have ceased to be outstanding; and

                      (j)    the term "SEC" means the Securities and Exchange
Commission.

               2.     Request for Registration.

                      (a)    Commencing on the Effective Date, if the Company
shall receive a written request (specifying that it is being made pursuant to
this Section 2) from the Holders of more than ten percent (10%) of the
Registrable Securities that the Company file a registration statement under the
1933 Act, or a similar document pursuant to any other statute then in effect
corresponding to the 1933 Act, covering the Registrable Securities that are the
subject of such request, then the Company shall file a registration statement
under the 1933 Act on an appropriate form (which form shall be available for the
sale of the Registrable Securities in accordance with the intended method or
methods of distribution) covering such Registrable Securities and shall use its
best efforts to cause all Registrable Securities that the Holders have requested
be registered to be registered under the 1933 Act; provided, however, that (i)
the Company shall not be obligated to prepare, file and cause to become
effective pursuant to this Section 2(a) a registration statement unless the
proposed aggregate public offering price of the securities to be included in
such registration statement is at least five million Dollars ($5,000,000) and
(ii) the rights of the Holders under this Section 2(a) shall be subject to the
provisions of the Lock-Up Agreements.

                      (b)    Notwithstanding the foregoing, if the Company shall
furnish to such Holders a certificate signed by the President or Chief Executive
Officer of the Company stating that, in the reasonable determination of the
Board of Directors of the Company, there exists circumstances not yet disclosed
to the public which would be required to be disclosed in a registration
statement filed pursuant to Section 2(a) and the disclosure of which would be
materially harmful to the Company or its stockholders, then the Company's
obligation to file such a registration statement shall be deferred for a period
not to exceed three (3) months;


                                       2
<PAGE>   3

provided, however, that the Company's right to defer the registration rights
provided hereunder pursuant to this Section 2(b) may be exercised only once.

                      (c)    The Company shall be obligated to effect only two
registrations pursuant to Section 2(a). Any request for registration under
Section 2(a) must be for a firmly underwritten public offering to be managed by
an underwriter or underwriters of recognized national standing selected by such
Holders, subject to the approval of the Board of Directors of the Company, which
approval shall not be unreasonably withheld.

               3.     Piggy-back Registration.

                      (a)    If at any time the Company proposes to register any
shares of its capital stock under the 1933 Act in connection with the public
offering of such securities solely for cash on a form that would also permit the
registration of the Registrable Securities (other than a registration statement
on Form S-4 or Form S-8 or any successor form thereof), the Company shall, each
such time, promptly give the Holders written notice of such determination. Upon
the written request of any Holders given within twenty (20) calendar days after
the delivery of any such notice by the Company, the Company shall include in
such registration statement all of the Registrable Securities that such Holder
has requested to be registered.

                      (b)    The Company may decline to file a registration
statement after giving notice to the Holders pursuant to Section 3(a) above, or
withdraw a registration statement after filing and after such notice, but prior
to the effectiveness thereof; provided that the Company shall promptly notify
the Holders in writing of any such action and provided further that the Company
shall bear all expenses incurred by any Holder in connection with such withdrawn
registration statement.

                      (c)    In connection with any offering involving an
underwriting of shares being issued by the Company, the Company shall not be
required under this Section 3 to include any of the Holders' Registrable
Securities in such underwriting unless each such Holder expressly accepts in
writing the terms of the underwriting as agreed upon between the Company and the
underwriters selected by it; provided that the underwriting agreement shall be
in customary form. If in the judgment of the managing underwriter of such
offering the inclusion of all of the Registrable Securities requested to be
registered would interfere with the successful marketing of shares in such
offering, then the number of Registrable Securities to be included in the
offering shall be reduced to such smaller number with the participation in such
offering to be in the following order of priority: (i) first, the shares of
capital stock which the Company proposes to sell for its own account and (ii)
second, the Registrable Securities requested to be included (to be allocated pro
rata among such Holders requesting such registration based upon the number of
Registrable Securities owned by such Holders); provided that the Registrable
Securities included shall not be reduced to less than 20% of the securities in
such offering. All Registrable Securities so excluded from the underwritten
public offering shall be withheld from the market by such Holders, for a period
(not to exceed 30 days prior to the effective date of such public offering and
120 days thereafter) that the managing underwriter reasonably determines is
necessary, in order to effect the underwritten public offering.


                                       3
<PAGE>   4

               4.     Obligations of the Company. If and whenever the Company is
required to register Registrable Securities under Section 2 or Section 3 above,
the Company shall use its best efforts to effect such registration to permit the
sale of such Registrable Securities in accordance with the intended plan of
distribution thereof, and pursuant thereto the Company will as expeditiously as
possible:

                      (a)    prepare and file with the SEC as soon as
practicable a registration statement with respect to such Registrable Securities
and use its best efforts to cause such registration statement to become
effective and remain continuously effective until the earlier to occur of (i)
the date six months from the date such registration statement was declared
effective, and (ii) the date the last of the Registrable Securities covered by
such registration statement have been sold, provided that before filing a
registration statement or prospectus or any amendments or supplements thereto,
the Company shall furnish to the Holders of the Registrable Securities covered
by such registration statement as well as the underwriters, if any, draft copies
of all such documents proposed to be filed at least 48 hours prior to filing,
which documents will be subject to the review of such Holders and underwriters,
and the Company shall not file any registration statement or amendment thereto
or any prospectus or any supplement thereto to which such Holders or the
underwriters, if any, shall reasonably object;

                      (b)    prepare and file with the SEC such amendments and
post-effective amendments to the registration statement, and such supplements to
the prospectus, as may be requested by any Holder of Registrable Securities
covered by such registration statement or any underwriter of Registrable
Securities or as may be required by the rules, regulations or instructions
applicable to the registration form used by the Company or by the 1933 Act or
rules and regulations thereunder to keep the registration statement effective
until all Registrable Securities covered by such registration statement are sold
in accordance with the intended plan of distribution set forth in such
registration statement or supplement to the prospectus;

                      (c)    promptly notify in writing the selling Holders of
Registrable Securities and the managing underwriter, if any,

                             (1)    when the prospectus or any supplement or
post-effective amendment has been filed, and, with respect to the registration
statement or any post-effective amendment, when the same has become effective,

                             (2)    of any request by the SEC for amendments or
supplements to the registration statement or the prospectus or for additional
information,

                             (3)    of the issuance by the SEC of any stop order
suspending the effectiveness of the registration statement or the initiation of
any proceedings for that purpose,

                             (4)    if at any time the representations and
warranties of the Company contemplated by clause (1) of Section 4(o) below cease
to be accurate in all material respects,


                                       4
<PAGE>   5

                             (5)    of the receipt by the Company of any
notification with respect to the suspension of the qualification of the
Registrable Securities for sale in any jurisdiction or the initiation or
threatening of any proceeding for such purpose, and

                             (6)    of the existence of any fact which results
in the registration statement, the prospectus or any document incorporated
therein by reference to contain a Misstatement.

                      (d)    make every reasonable effort to obtain the
withdrawal of any order suspending the effectiveness of the registration
statement at the earliest possible time;

                      (e)    if requested by the managing underwriter or a
Holder of Registrable Securities being sold in an underwritten offering,
immediately incorporate in a supplement or post-effective amendment such
information as the managing underwriter and the Holders of a majority of
Registrable Securities being sold agree should be included therein relating to
the sale of the Registrable Securities, including, without limitation,
information with respect to the number of shares of Registrable Securities being
sold to underwriters, the purchase price being paid therefor by such
underwriters and with respect to any other terms of the underwritten offering of
the Registrable Securities to be sold in such offering, and make all required
filings of such supplement or post-effective amendment as soon as notified of
the matters to be incorporated in such supplement or post-effective amendment;

                      (f)    promptly prior to the filing of any document which
is to be incorporated by reference into the registration statement or the
prospectus provide copies of such document to counsel to the selling Holders of
Registrable Securities and to the managing underwriter, if any, and make the
Company's representatives available for discussion of such document and make
such changes in such document prior to the filing thereof as counsel for the
selling Holders of Registrable Securities or underwriters may reasonably
request;

                      (g)    furnish to each selling Holder of Registrable
Securities and the managing underwriter, without charge, at least one signed
copy of the registration statement and any post-effective amendments thereto,
including financial statements and schedules, all documents incorporated therein
by reference and all exhibits (including those incorporated by reference);

                      (h)    deliver to each selling Holder of Registrable
Securities and the underwriters, if any, without charge, as many copies of each
prospectus (and each preliminary prospectus) as such persons may reasonably
request (the Company hereby consenting to the use of each such prospectus (or
preliminary prospectus) by each selling Holder of Registrable Securities and the
underwriters, if any, in connection with the offering and sale of the
Registrable Securities covered by such prospectus (or preliminary prospectus);

                      (i)    prior to any public offering of Registrable
Securities, register or qualify or cooperate with the selling Holders of
Registrable Securities, the underwriters, if any, and their respective counsel
in connection with the registration or qualification of such Registrable
Securities for offer and sale under the securities or blue sky laws of such
jurisdictions as such selling Holder of Registrable Securities or underwriters
may designate in


                                       5
<PAGE>   6

writing and do anything else necessary or advisable to enable the disposition in
such jurisdictions of the Registrable Securities covered by the registration
statement, provided that the Company shall not be required to qualify generally
to do business in any jurisdiction where it is not then so qualified or to take
any action which would subject it to general service of process in any such
jurisdiction where it is not then so subject;

                      (j)    cooperate with the selling Holders of Registrable
Securities and the managing underwriter, if any, to facilitate the timely
preparation and delivery of certificates not bearing any restrictive legends
representing the Registrable Securities to be sold and cause such Registrable
Securities to be in such denominations and registered in such names as the
managing underwriter may request at least three business days prior to any sale
of Registrable Securities to the underwriters;

                      (k)    use its best efforts to cause the Registrable
Securities covered by the registration statement to be registered with or
approved by such other governmental agencies or authorities as may be necessary
to enable the seller or sellers thereof or the underwriters, if any, to
consummate the disposition of such Registrable Securities;

                      (l)    if the registration statement or the prospectus
contains a Misstatement, prepare a supplement or post-effective amendment to the
registration statement or the related prospectus or any document incorporated
therein by reference or file any other required document so that, as thereafter
delivered to the purchasers of the Registrable Securities, the prospectus will
not contain a Misstatement;

                      (m)    cause all Registrable Securities covered by the
registration statement to be listed on any national securities exchange or
authorized for quotation on NASDAQ or in the National Market System if requested
by the Holders of a majority of such Registrable Securities or the managing
underwriter, if any;

                      (n)    provide a CUSIP number for all Registrable
Securities not later than the effective date of the Registration Statement;

                      (o)    enter into such agreements (including an
underwriting agreement) and do anything else necessary or advisable in order to
execute or facilitate the disposition of such Registrable Securities, and in
such connection, whether or not the registration is an underwritten
registration:

                             (1)    make such representations and warranties to
the selling Holders of Registrable Securities and the underwriters, if any, in
form, substance and scope as are customarily made by issuers to underwriters in
primary underwritten offerings;

                             (2)    obtain opinions of counsel to the Company
and updates thereof (which counsel and opinions (in form, scope and substance)
shall be reasonably satisfactory to the managing underwriter, if any, and the
Holders of a majority of Registrable Securities being sold) addressed to each
selling Holder and the underwriter, if any, covering the matters customarily
covered in opinions delivered to underwriters in primary underwritten offerings
and such other matters as may be reasonably requested by such Holders or
underwriters.


                                       6

<PAGE>   7

                             (3)    obtain "cold comfort" letters and updates
thereof from the Company's independent certified accountants addressed to the
selling Holders of such Registrable Securities and the underwriters, if any,
such letters to be in customary form and covering matters of the type
customarily covered in "cold comfort" letters by underwriters in connection with
the primary underwritten offerings;

                             (4)    if an underwriting agreement is entered
into, cause the same to include the indemnification and contribution provisions
and procedures of Section 7 hereof with respect to all parties to be indemnified
pursuant to said Section 7 (or, with respect to the indemnification of such
underwriters, such similar indemnification and contribution provisions as such
underwriters shall customarily require); and

                             (5)    deliver such documents and certificates as
may be reasonably requested by the Holders of a majority of Registrable
Securities being sold and the managing underwriter, if any, to evidence
compliance with clause (1) above and with any customary conditions contained in
the underwriting agreement or other agreement entered into by the Company.

Each of the actions to be taken under this Section 4(o) shall be taken at each
closing under such underwriting or similar agreement or as and to the extent
otherwise reasonably requested by the Holders of a majority of Registrable
Securities being sold,

                      (p)    make available for inspection by representatives of
the Holders of a majority of Registrable Securities being sold, any underwriter
participating in any disposition pursuant to such registration statement, and
any attorney or accountant retained by the selling Holders or any such
underwriter, all financial and other records and pertinent corporate documents
and properties of the Company, and cause the Company's officers, directors and
employees to supply all information reasonably requested by any such
representative, underwriter, attorney or accountant in connection with the
registration; provided that any records, information or documents that are
designated by the Company in writing as confidential shall be kept confidential
by such persons unless disclosure of such records, information or documents is
required by a court or administrative order; and

                      (q)    otherwise use its best efforts to comply with all
applicable rules and regulations of the SEC.

               5.     Condition Precedent. It shall be a condition precedent to
the obligations of the Company to take any action pursuant hereto that the
Holders shall furnish to the Company such information regarding them, the
Registrable Securities held by them, and the intended method of disposition of
such Registrable Securities as the Company shall reasonably request and as shall
be required in connection with the action to be taken by the Company.

               6.     Expenses of Registration. All expenses incurred in
connection with any registrations pursuant to Section 2 hereof, including
without limitation all registration and qualification fees, printers' and
accounting fees, reasonable fees and disbursements of counsel for the Company,
and fees and disbursements of counsel for the selling Holders shall be borne by
such Holders. All expenses incurred in connection with any registrations
pursuant to Section 3

                                       7

<PAGE>   8

hereof, including without limitation all registration and qualification fees,
printers' and accounting fees and fees and disbursements of counsel for the
Company shall be borne by the Company, except that the selling Holders shall be
responsible for the fees and disbursements of their counsel and the underwriting
discounts and commissions and transfer taxes in connection with any Registrable
Securities included in a registration statement pursuant to Section 3 hereof.

               7.     Indemnification. In the event any Registrable Securities
are included in a registration statement hereunder:

                      (a)    To the extent permitted by law, the Company will
indemnify and hold harmless each Holder requesting or joining in a registration,
any underwriter (as defined in the 1933 Act) for the Holders, and each person,
if any, who controls such Holder or underwriter within the meaning of the 1933
Act (the "Holder Indemnified Parties"), against any losses, claims, damages, or
liabilities, joint or several, to which any Holder Indemnified Party may become
subject under the 1933 Act, the 1934 Act or otherwise, insofar as such losses,
claims, damages, or liabilities (or actions in respect thereof) arise out of or
are based on any Misstatement in such registration statement, including any
preliminary prospectus or final prospectus contained therein or any amendments
or supplements thereto, or arise out of any violation by the Company of any rule
or regulation promulgated under the 1933 Act or 1934 Act applicable to the
Company and relating to action or inaction required of the Company in connection
with any such registration. The Company will reimburse each such Holder
Indemnified Party for any legal or other expenses reasonably incurred by them in
connection with investigating or defending any such loss, claim, damage,
liability, or action. Notwithstanding anything to the contrary contained in this
Section 7(a), the indemnity agreement contained in this paragraph 7(a) shall not
(i) apply to amounts paid in settlement of any such loss, claim, damage,
liability, or action if such settlement is effected without the consent of the
Company (which consent shall not be unreasonably withheld); (ii) apply to any
such case for any such loss, claim, damage, liability, or action to the extent
that it (A) arises out of or is based upon a Misstatement made in connection
with such registration statement, preliminary prospectus, final prospectus, or
amendments or supplements thereto, in reliance upon and in conformity with
written information furnished expressly for use in connection with such
registration by any such Holder Indemnified Party, or (B) arises out of any
violation by any such Holder Indemnified Party of any rule or regulation
promulgated under the 1933 Act or the 1934 Act applicable to such Holder
Indemnified Party, and relating to action or inaction required of such Holder
Indemnified Party, in connection with any such registration; or (iii) inure to
the benefit of any underwriter from whom the person asserting any such loss,
claim, damage or liability purchased the Registrable Securities which are the
subject thereof (or to the benefit of any person controlling such underwriter)
with respect to a preliminary prospectus or final prospectus if such underwriter
(if required by the 1933 Act or the 1934 Act) failed to send or give a copy of
the most recent prospectus, if the most recent prospectus furnished by the
Company corrected the Misstatement or alleged Misstatement which is the basis of
the loss, claim, damage, liability, or action for which indemnification is
sought, to such person at or prior to the written confirmation of the sale of
such Registrable Securities to such person. This indemnity will be in addition
to any liability which the Company may otherwise have.

                      (b)    To the extent permitted by law, each Holder
requesting or joining in a registration will indemnify and hold harmless the
Company, each of its directors, each of its

                                       8

<PAGE>   9

officers who have signed the registration statement, each person, if any, who
controls the Company within the meaning of the 1933 Act, and each agent and any
underwriter for the Company (within the meaning of the 1933 Act) (the "Company
Indemnified Parties") against any losses, claims, damages, or liabilities to
which any Company Indemnified Party may become subject, under the 1933 Act, the
1934 Act, or otherwise, insofar as such losses, claims, damages, or liabilities
(or actions in respect thereto) (A) arise out of or are based upon any
Misstatement in such registration statement, including any preliminary
prospectus or final prospectus contained therein or any amendments or
supplements thereto, in each case to the extent, but only to the extent, that
such Misstatement or alleged Misstatement was made in such registration
statement, preliminary or final prospectus, or amendments or supplements
thereto, in reliance upon and in conformity with written information furnished
by such Holder expressly for use in connection with such registration, or (B)
arise out of any violation by such Holder of any rule or regulation promulgated
under the 1933 Act or the 1934 Act applicable to such Holder and relating to
action or inaction required of such Holder in connection with any such
registration. Each such Holder will reimburse any legal or other expenses
reasonably incurred by such Company Indemnified Party in connection with
investigating or defending any such loss, claim, damage, liability, or action.
Notwithstanding anything to the contrary contained in this Section 7(b), the
indemnity agreement contained in this Section 7(b) shall not (i) apply to
amounts paid in settlement of any such loss, claim, damage, liability, or
action if such settlement is effected without the consent of such Holder (which
consent shall not be unreasonably withheld); or (ii) inure to the benefit of
any underwriter from whom the person asserting any such loss, claim, damage or
liability purchased the Registrable Securities which are the subject thereof
(or to the benefit of any person controlling such underwriter) with respect to
a preliminary prospectus or final prospectus if such underwriter (if required
by the 1933 Act or 1934 Act) failed to send or give a copy of the most recent
prospectus, if the most recent prospectus furnished by the Company corrected
the Misstatement or alleged Misstatement which is the basis of the loss, claim,
damage, liability, or action for which indemnification is sought, to such
person at or prior to the written confirmation of the sale of such Registrable
Securities to such person. This indemnity will be in addition to any liability
which each Holder may otherwise have.

                      (c)    If the indemnification provided for in this Section
7 is unavailable to an indemnified party under Section 7(a) or Section 7(b)
above (other than by reason of exceptions provided in those Sections) in respect
of any losses, claims, damages, or liabilities referred to in such Sections,
then each applicable indemnifying party, in lieu of indemnifying such
indemnified party, shall contribute to the amount paid or payable by such
indemnified party as a result of such losses, claims, damages, or liabilities in
such proportion as is appropriate to reflect the relative fault of the
indemnifying party on the one hand and of the indemnified party on the other in
connection with the statements or omissions which resulted in such losses,
claims, damages, or liabilities as well as any other relevant equitable
considerations. The amount paid or payable by a party as a result of the losses,
claims, damages, or liabilities referred to above shall be deemed to include,
subject to the limitations set forth in Section 7(d), any legal or other fees or
expenses reasonably incurred by such party in connection with investigating or
defending any action or claim. The relative fault of the indemnified party on
the one hand and of the indemnifying party on the other shall be determined by
reference to, among other things, whether the Misstatement or alleged
Misstatement relates to information supplied by the indemnified party or the
indemnifying party and the parties' relative intent, knowledge, access to
information and opportunity to correct or prevent such Misstatement or alleged
Misstatement. The Company



                                       9
<PAGE>   10

and the Stockholders agree that it would not be just and equitable if
contribution pursuant to this Section 7(c) were determined by pro rata
allocation or by any other method of allocation which does not take account of
the equitable considerations referred to above. Notwithstanding the provisions
of this Section 7(c), a Holder Indemnified Party shall not be required to
contribute any amount in excess of the amount by which (i) the total price at
which the securities that were sold by such Holder Indemnified Party and
distributed to the public were offered to the public exceeds (ii) the amount of
any damages which such Holder Indemnified Party has otherwise been required to
pay by reason of such Misstatement. No person guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be
entitled to contribution from any person who was not guilty of such fraudulent
misrepresentation.

                      (d)    Any person entitled to indemnification hereunder
will: (i) give prompt notice to the indemnifying party of any claim with respect
to which it seeks indemnification; and (ii) unless in such indemnified party's
reasonable judgment a conflict of interest between such indemnified and
indemnifying parties may exist with respect to such claim, permit such
indemnifying party to assume the defense of such claim with counsel reasonably
satisfactory to the indemnified party. If such defense is assumed, the
indemnifying party will not be subject to any liability for any settlement made
without its consent (but such consent will not be unreasonably withheld). An
indemnifying party who is not entitled or elects not to assume the defense of a
claim will not be obligated to pay the fees and expenses of more than one
counsel for all parties indemnified by such indemnifying party with respect to
such claim, unless in the reasonable judgment of any indemnified party a
conflict of interest may exist between such indemnified party and any other such
indemnified parties with respect to such claim. The failure to notify an
indemnifying party promptly of the commencement of any such action, if
prejudicial to his ability to defend such action, shall relieve such
indemnifying party of any liability to the indemnified party under this
paragraph, but the omission so to notify the indemnifying party will not relieve
him of any liability that he may have to any indemnified party otherwise than
under this Section.

               8.     Termination of the Company's Obligations. The Company
shall have no obligations pursuant to Section 2 or Section 3 with respect to any
request or requests made by a Holder of Registrable Securities more than five
(5) years after the Effective Date.

               9.     Reports Under the 1934 Act. With a view to making
available to the Holders the benefits of Rule 144 promulgated under the 1933 Act
and any other rule or regulation of the SEC that may at any time permit a Holder
to sell securities of the Company to the public without registration, the
Company agrees to use its best efforts to:

                      (a)    make and keep public information available, as
those terms are understood and defined in Rule 144, at all times subsequent to
ninety (90) days after the Effective Date;

                      (b)    file with the SEC in a timely manner all reports
and other documents required of the Company under the 1933 Act and the 1934 Act;
and

                      (c)    Furnish to any Holder forthwith upon request (i) a
written statement by the Company that it has complied with the reporting
requirements of Rule 144 (at


                                       10

<PAGE>   11

any time after ninety (90) days after the Effective Date), and of the 1933 Act
and the 1934 Act (at any time after it has become subject to such reporting
requirements), (ii) a copy of the most recent annual or quarterly report of the
Company, and (iii) such other reports and documents so filed by the Company as
may be reasonably requested in availing any Holder of any rule or regulation of
the SEC permitting the selling of any such securities without registration.

               10.    Transfer of Registration Rights. The registration rights
of the Holders hereunder may be transferred to any transferee who is (i) a
nominee of such Holder or a trust of which such Holder is the Trustor so long as
the beneficial owner of the Registrable Securities being transferred remains the
same, (ii) an entity controlled by such Holder, or (iii) a shareholder or
partner, as the case may be, of any Holder, if such shareholder or partner
receives Registrable Securities from such Holder as a dividend or other
distribution. The Company shall be given written notice by the Holder at the
time of any transfer stating the name and address of any transferee and
identifying the securities with respect to which the rights hereunder are being
transferred.

               11.    No Inconsistent Agreements. Other than the Lock-Up
Agreements, the Company shall not on or after the date of this Agreement enter
into any agreement with respect to its securities that is inconsistent with the
rights granted to the Holders in this Agreement or otherwise conflicts with the
provisions hereof.

               12.    Amendments and Waivers. The provisions of this Agreement,
including the provisions of this sentence, may not be amended, modified or
supplemented, and waivers or consents to departures from the provisions hereof
may not be given, without the prior written consent of the Company and at least
the Holders of a majority of the Registrable Securities. The foregoing
notwithstanding, a waiver or consent to departure from the provisions hereof
that relates exclusively to the rights of Holders of Registrable Securities
whose Registrable Securities are being sold pursuant to a registration statement
and that does not directly or indirectly affect the rights of other Holders of
Registrable Securities may be given by the Holders of a majority of Registrable
Securities being sold.

               13.    Notices.  All notices provided for in this Agreement shall
be validly given if in writing and (i) delivered personally or (ii) sent by
registered mail, postage prepaid, return receipt registered to the address set
forth below:

        If to the Company:

               The Advisory Board Company
               The Watergate
               600 New Hampshire Avenue, N.W.
               Washington, D.C.  20037
               Attn.: David Felsenthal

        If to the Stockholders:

               c/o The Advisory Board Company
               The Watergate
               600 New Hampshire Avenue, N.W.


                                       11

<PAGE>   12

               Washington, D.C.  20037
               Attn.: David Felsenthal

               or to such other address as the parties may, from time to time,
designate in a written notice given in a like manner to the other parties
hereto. Notice given in person shall be deemed delivered when received (or when
delivery is first refused) and notice given by mail shall be deemed delivered
five (5) calendar days after the date mailed.. The Company shall promptly
provide a list of the most current addresses of the Holders of Registrable
Securities given to it in accordance with the provisions hereof to any such
Holder for the purpose of enabling such Holder to communicate with other Holders
in connection with this Agreement.

               14.    Successors and Assigns. This Agreement shall inure to the
benefit of and be binding upon the successors and assigns of each of the
parties.

               15.    Counterparts. This Agreement may be executed in any number
of counterparts and by the parties hereto in separate counterparts, each of
which when so executed shall be deemed to be an original and all of which taken
together shall constitute one and the same agreement.

               16.    Governing Law.  This Agreement shall be governed by and
construed in accordance with the laws of the State of Delaware without giving
effect to the conflict of laws provisions thereof.

               17.    Severability. In the event that any one or more of the
provisions contained herein, or the application thereof in any circumstance, is
held invalid, illegal or unenforceable, the validity, legality and
enforceability of any such provision in every other respect and of the remaining
provisions contained herein shall not be affected or impaired thereby, but only
to the extent that giving effect to such provision and the remainder of the
terms and provisions hereof shall be in accordance with the intent of the
parties.

               18.    Forms. All references in this Agreement to particular
forms of registration statements are intended to include all successor forms
which are intended to replace, or to apply to similar transactions as, the forms
herein referenced.

               19.    Entire Agreement. This Agreement is intended by the
parties as the final expression of their agreement and intended to be a complete
and exclusive statement of the agreement and understanding of the parties hereto
in respect of the subject matter contained herein. There are no restrictions,
promises, warranties or undertakings, other than those set forth or referred to
herein with respect to the registration rights granted by the Company with
respect to the Registrable Securities. This Agreement supersedes all prior
agreements and understandings between the parties with respect to such subject
matter.

                            [Signature page follows.]



                                       12

<PAGE>   13



               IN WITNESS WHEREOF, the parties hereto have caused this
Registration Rights Agreement to be duly executed, as of the day and year first
above written.

                                           THE ADVISORY BOARD COMPANY



                                           By:  /s/ FRANK WILLIAMS
                                               ---------------------------------
                                           Name:  Frank Williams
                                           Title:  Chief Executive Officer



                                               /s/ DAVID G. BRADLEY
                                               ---------------------------------
                                               David G. Bradley

                                               /s/ JEFFREY D. ZIENTS
                                               ---------------------------------
                                               Jeffrey D. Zients

                                               /s/ MICHAEL D'AMATO
                                               ---------------------------------
                                               Michael D'Amato



                                       13