Document:

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                                                                   EXHIBIT 10.6

                             STOCK OPTION AGREEMENT

        THIS STOCK OPTION AGREEMENT (this "Option Agreement") is made effective
as of May 1, 2001 (the "Effective Date"), between David G. Bradley ("DGB") and
the Advisory Board Company (the "Company"), granting to the Company Options to
purchase 6,775,625 shares (the "Option Shares") of the Company's Class B
Nonvoting Common Stock, par value $0.01 per share (the "Stock"), at a purchase
price of $4.80 per Option Share, as further described in Section 2 below.

                                 R E C I T A L S

        WHEREAS, DGB owns 20,725,000 shares of the Stock;

        WHEREAS, the Company has granted options (the "Third Party Options") to
purchase shares of its Stock to certain employees of the Company; and

        WHEREAS, upon the sale and issuance by the Company of Stock pursuant to
option exercises under the Third Party Options, DGB and the Company desire that
the Company purchase shares of Stock from DGB, subject to the terms and
conditions of this Option Agreement.

        NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties agree as follows:

        1.      GRANT OF OPTION. DGB hereby grants to the Company the right and
option (the "Option" or "Options") to purchase from DGB, on the terms and
conditions hereinafter set forth, all or any part of an aggregate number of
Option Shares as described in the preamble (the outstanding amount of such
unexercised and unexpired Options shall herein be referred to as the "Option
Number"), at the purchase price per Option Share as described in the preamble
(as such amount may be adjusted as herein provided, the "Exercise Price"), on
the terms and conditions set forth herein.

        2.      EXERCISABILITY. The Options shall only be exercisable by the
Company either (a) in one-third increments on each of the first three
anniversary dates of either an initial public offering, approved sale of stock,
or approved sale of assets of the Company, or (b) on the tenth anniversary of
the Effective Date in the event none of the transactions listed in (a) above
have occurred.

        3.      EXPIRATION. The number of Option Shares that the Company is
entitled to purchase pursuant to the Options shall be decreased by the number of
Option Shares purchased hereunder by the Company on any given date. Any
unexercised Options shall expire on May 31, 2011.

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        4.      EXERCISE OF THE OPTION.

        (a)     Prior to expiration, the Company may exercise the Options from
time to time in whole or in part as permitted hereunder (the "Exercise Date").
On the Exercise Date, the Company shall deliver to DGB the following:

                (i)     A written and signed notice of such election setting
        forth the number of Option Shares the Company has elected to purchase;

                (ii)    Payment in full of the aggregate Exercise Price of such
        Option Shares in cash, a cashier's or certified bank check payable to
        the order of DGB or wire transfer of immediately available funds to the
        account of DGB.

        (b)     Notwithstanding anything in Section 4(a) to the contrary, DGB
                may, in his sole and absolute discretion, permit payment of the
                Exercise Price in such form or in such manner as may be
                otherwise permissible under any applicable law.

        5.      LIQUIDATION OF THE OPTION. DGB may liquidate the Option at any
point, at his discretion, by transferring consideration to the Company equal to
the fair value of the Option in excess of the purchase price. The fair value of
the option shall be determined by an investment bank selected by the Company, in
its sole and absolute discretion. The investment bank shall use customary
criteria generally employed within the investment banking community for valuing
the assets or capital stock of an entity similar to the Company. In the event of
a public offering of stock pursuant to the Securities Act of 1933 and the
Securities Act of 1934, the initial public offering price of common stock sold
in the offering shall constitute fair value. The consideration transferred may
be in the form of cash or stock of the Company owned by DGB.

        6.      CANCELLATION OF THE OPTION. This Option Agreement may be
cancelled at any time if mutually agreed upon by both parties in writing.

        7.      NONTRANSFERABILITY. The Option shall not be transferable by the
Company.

        8.      ADJUSTMENTS. If the shares of the Stock are changed into or
exchanged for a different number or kind of shares or securities, as the result
of any one or more reorganizations, recapitalizations, mergers, acquisitions,
stock splits, reverse stock splits, stock dividends or similar events, an
appropriate adjustment shall be made in the number and kind of shares or other
securities subject to the Option, and the price for each share or other unit of
any securities subject to this Option Agreement. No fractional interests shall
be issued on account of any such adjustment unless DGB specifically determines
to the contrary; provided, however, that in lieu of fractional interests, the
Company, upon the exercise of the Option in whole or part, shall receive cash in
an amount equal to the amount by which the fair market value (as reasonably
agreed to between the Company and DGB) of such fractional interests exceeds the
Exercise Price attributable to such fractional interests.

        9.      BINDING EFFECT. This Option Agreement shall inure to the benefit
of and be binding upon the parties hereto and their respective permitted
successors and assigns.

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        10.     ENTIRE OPTION AGREEMENT. This Option Agreement and the documents
referred to herein set forth the entire agreement and understanding between the
parties as to the subject matter hereof and supersedes all prior oral and
written and all contemporaneous oral discussions, agreements and understandings
of any kind or nature.

        11.     AMENDMENTS AND WAIVERS. This Option Agreement may be amended,
and any provision hereof may be waived, only by a writing signed by the parties
hereto.

        12.     HEADINGS. The headings preceding the text of the sections hereof
are inserted solely for convenience of reference, and shall not constitute a
part of this Option Agreement, nor shall they affect its meaning, construction
or effect.

        13.     GOVERNING LAW. All terms of and rights under this Option
Agreement shall be governed by and construed in accordance with the internal law
of the State of Maryland, without giving effect to principles of conflicts of
law.

        IN WITNESS WHEREOF, the parties have executed this Option Agreement
effective as of the Effective Date.

                                            /s/DAVID G. BRADLEY
                                            --------------------------
                                            DAVID G. BRADLEY

                                            THE ADVISORY BOARD COMPANY

                                            By: /s/Michael D'Amato
                                               ---------------------------
                                            Name:    Michael D'Amato
                                            Title:   Executive Vice President

                                        3<PAGE>   1

                                                                    EXHIBIT 10.7

                           THE ADVISORY BOARD COMPANY
                                  THE WATERGATE
                         600 NEW HAMPSHIRE AVENUE, N.W.
                             WASHINGTON, D.C. 20037

                                  May 31, 2001

Mr. Jeffrey D. Zients
c/o The Advisory Board Company
600 New Hampshire Avenue, N.W.
Washington, D.C.  20037

               Re:    Stock Option Agreement Number 1 between The Advisory Board
                      Company and Jeffrey D. Zients (the "Agreement")

Dear Mr. Zients:

        Pursuant to Section 3(a) of the Agreement, David G. Bradley, as Chairman
of the Board of The Advisory Board Company, hereby designates May 29, 2001 as
the date on which all of the unvested Options granted to you pursuant to the
Agreement (the "Options") shall be immediately vested. Pursuant to Section 4(a)
of the Agreement, the Advisory Board Company has determined that all of your
Options shall be exercisable on May 30, 2001.

                                            Very truly yours,

                                            /s/David G. Bradley
                                            ---------------------------
                                            David G. Bradley
                                            Chairman of the Board
                                            The Advisory Board Company

                                            /s/David G. Bradley
                                            ----------------------------
                                            The Advisory Board Company
                                            By:  David G. Bradley

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                           THE ADVISORY BOARD COMPANY

                NOTICE OF EXERCISE FOR NON-QUALIFIED STOCK OPTION

Option Grant Date:                November 1, 1997
Option Price:                     $1.96 (split adjusted)
Original Number of Optioned
Shares Granted:                   1,436,550 (split adjusted)

        EXERCISE OF OPTION.  Optionee hereby exercises his option to purchase
750,000 of his Optioned Shares.

        Optionee acknowledges that s/he understands that this Option is a
Non-Qualified Stock Option, meaning that it is not eligible for tax deferral,
and accordingly that:

        -       Optionee will owe taxes on the difference between the Option
                Price and the Company's stock price on the date of exercise; and

        -       Optionee must pay over to the Company an amount required to
                satisfy withholding tax obligations on the date of this Option
                exercise.

        Optionee hereby delivers, together with this written statement of
exercise, the full Option Price and tax withholding amount with respect to the
exercised Optioned Shares, which consists of [COMPLETE ONE OR MORE AS
APPLICABLE]

<TABLE>
<CAPTION>
 EXERCISE     WITHHOLDING
   PRICE          TAX
 --------     -----------
<S>           <C>            <C>
    [ ]           [X]        Cash in the total amount of $511,219.

    [ ]           [ ]        _____ shares of the Company's Common Stock.

    [ ]           [ ]        If acceptable to the Company in its sole
                             discretion, arrangements with the following
                             brokerage firm to pay over the exercise price
                             _______________________ _______________________
                             (firm name, contact and phone number)

    [X]           [ ]        Secured Promissory Note in the amount of:  $1,470,000
</TABLE>

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        ACKNOWLEDGEMENT. Optionee hereby acknowledges that, to the extent he is
an "affiliate" of the Company (as that term is defined in Rule 144 promulgated
under the Securities Act of 1933, as amended) or to the extent that the Optioned
Shares have not been registered under the Securities Act of 1933, as amended, or
applicable state securities laws, any shares of the Company's Common Stock
acquired by him as a result of his exercise of the Option pursuant to this
Notice are subject to, and the certificates representing such shares shall be
legended to reflect, certain trading restrictions under applicable securities
laws (including particularly the Securities and Exchange Commission's Rule 144),
all as described in Section 9 of the Plan, and Optionee hereby agrees to comply
with all such restrictions and to execute such documents or take such other
actions as the Company may require in connection with such restrictions.

<TABLE>
<CAPTION>
<S>                                               <C>
EXECUTED this 31st day of May, 2001               THE ADVISORY BOARD COMPANY
OPTIONEE:                                         hereby acknowledges receipt of
                                                  this Notice of Exercise and
                                                  receipt of payment in the form
                                                  and amount indicated above,
/s/ JEFFREY D. ZIENTS                             all on this 31st
--------------------------------------------      day of May, 2001.
Signature                                         THE ADVISORY BOARD COMPANY

Jeffrey D. Zients                                 By: /s/ DAVID G. BRADLEY
--------------------------------------------         ---------------------------------
Print or Type Name
                                                  David G. Bradley
                                                  ------------------------------------
                                                  Print or Type Name

                                                  Title:     Chairman
                                                          ----------------------------
</TABLE>

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[THE ADVISORY BOARD COMPANY LETTERHEAD]

                                 July 30, 2001

Jeffrey D. Zients
C/O The Advisory Board Company
600 New Hampshire Ave. NW
Washington, DC 20037

        Re:    May 31, 2001 exercise of stock options

Dear Jeffrey,

        On May 31, 2001, you exercised options to purchase shares of the
Class B Non-voting Common Stock of The Advisory Board Company. For the purposes
of the documentation associated with this exercise of options, the number of
shares of stock issued to you was calculated based on our assumption that we had
completed a 25-to-one stock split effective as of January 2, 2001. We recently
discovered that this stock split was not properly completed. Therefore, the
number of shares of stock set forth in the documentation associated with your
May 31, 2001 exercise of stock options is incorrect. The actual number of shares
of stock you received from us on May 31, 2001 may be calculated by dividing the
number of shares of stock set forth in such documentation by 25. Because the
failure to complete the 25-to-one stock spilt had the same effect on all
stockholders and optionholders, the foregoing recalculation does not change your
relative ownership interest in the equity of The Advisory Board Company.

        Within the next few weeks, we plan to complete the 25-to-one stock
split which we originally intended to be effective as of January 2, 2001. After
the effective date of this stock split, the number of shares of stock issued
pursuant to your May 31, 2001 exercise of options will equal the number of
shares of stock originally set forth in the documentation associated with that
exercise of options.

        Please indicate your agreement with and acceptance of the terms of this
letter by executing and returning the enclosed duplicate copy of this letter.

                                          Very truly yours,

                                          /s/ DAVID FELSENTHAL
                                          ------------------------
                                          David Felsenthal
                                          Chief Financial Officer

Agreed and Accepted:

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

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