<PAGE>

                                                                    EXHIBIT 99.3

                             STOCKHOLDER AGREEMENT


     This STOCKHOLDER AGREEMENT (the "Agreement"), dated as of August _____,
2000, is among PREMIER CONSTRUCTION PRODUCTS STATUTORY TRUST, a Connecticut
statutory trust ("Trust"), PREMIER CONSTRUCTION PRODUCTS ACQUISITION CORP., a
Delaware corporation and a wholly owned subsidiary of Trust ("Merger Sub"), and
_________________ (the "Stockholder"), a stockholder of Republic Group
Incorporated, a Delaware corporation (the "Company").


                             W I T N E S S E T H:


     WHEREAS, concurrently with the execution hereof, Trust, Merger Sub and the
Company are entering into an Agreement and Plan of Merger, dated as of the date
hereof, upon the terms and subject to the conditions of which Merger Sub will be
merged with and into the Company;

     WHEREAS, the Stockholder is the record and beneficial owner of ________
shares of Company Common Stock (collectively, the "Existing Shares"); and

     WHEREAS, in order to induce the Trust and Merger Sub to enter into the
Merger Agreement and consummate the transactions contemplated thereby, the
Stockholder is willing to enter into this Agreement in order to provide for,
among other things, (i) the obligation of Stockholder to vote, or cause the
record holder of the Shares to vote, the Shares that entitle the holder to vote
on any matter submitted to the stockholders of the Company (other than Shares
subject to unexercised options) (the "Voting Shares") in the manner specified
herein and, in connection therewith, to grant a proxy with respect to the Voting
Shares and (ii) certain restrictions on the sale, conveyance or transfer of the
Shares by the Stockholder; and

     NOW, THEREFORE, in consideration of the premises, the terms and provisions
set forth herein, the mutual benefits to be gained by the performance thereof
and other good and valuable consideration, the receipt and sufficiency of which
are hereby acknowledged, the parties hereto agree as follows:

     SECTION 1.  Defined Terms.

     (a) As used herein, the terms set forth below shall have the following
respective meanings:

     "beneficial owner" has the meaning set forth in Rule 13d-3 under the
Exchange Act, and the term "beneficial ownership" shall have a correlative
meaning.
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     "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     "Merger Agreement" means the Agreement and Plan of Merger of even date
herewith among the Trust, the Merger Sub and the Company, as the same may be
amended from time to time; provided, however, that such term shall not include
                           --------  -------
any amendment to such Agreement that decreases the price per share, or changes
the form of consideration, payable in respect of the Shares, unless the
Stockholder consents to the inclusion of such amendment in such term.

     "Shares" means the Existing Shares, together with all other shares of
capital stock or voting securities of the Company of which the Stockholder is a
direct or indirect beneficial owner as of the date of this Agreement, and any
other shares of capital stock or voting securities of the Company of which the
Stockholder becomes the direct or indirect beneficial owner after the date
hereof, including, but not limited to, shares or voting securities received
pursuant to any stock splits, stock dividends or distributions, shares or voting
securities acquired by purchase or upon the exercise, conversion or exchange of
any option, warrant or convertible security or otherwise and shares or voting
securities received pursuant to any change in the capital stock of the Company
by reason of any recapitalization, merger, reorganization, consolidation,
combination, exchange of shares or any transaction with like purpose or effect.

     (b) Capitalized terms used herein without definition shall have the
respective meanings assigned to such terms in the Merger Agreement.

     SECTION 2.  Agreement to Vote. For so long as this Agreement remains in
effect (the "Term"), the Stockholder shall, at any meeting of the stockholders
of the Company (including, but not limited to, the Company Stockholder Meeting),
and in any action by written consent of the stockholders of the Company in lieu
of a meeting, vote all of the Voting Shares (i) in favor of the Merger Agreement
and the Merger and the other transactions contemplated by the Merger Agreement
and (ii) against any Takeover Proposal or any agreement, arrangement or
transaction relating to any Takeover Proposal or required in order to implement
the same or any other action or agreement that, directly or indirectly, is
inconsistent with the Merger Agreement or the transactions contemplated thereby
or that is reasonably likely (a) to impede, interfere with, delay or postpone
the Merger or the other transactions contemplated by the Merger Agreement, (b)
to result in a breach of any covenant, representation, warranty or any other
obligation of Company under the Merger Agreement or (c) to cause any conditions
to the obligations of the parties under the Merger Agreement not to be
fulfilled.

     SECTION 3.  PROXY. THE STOCKHOLDER HEREBY GRANTS TO, AND APPOINTS, EACH OF
DOUGLAS H. WOLF AND RICHARD G. BUCKINGHAM, IN THEIR RESPECTIVE CAPACITIES AS
OFFICERS OF MERGER SUB, AND ANY INDIVIDUAL WHO SHALL HEREAFTER SUCCEED TO THE
OFFICE NOW HELD BY ANY SUCH OFFICER OF MERGER SUB, AND ANY OTHER PERSON
DESIGNATED IN WRITING BY MERGER SUB, EACH OF THEM INDIVIDUALLY, STOCKHOLDER'S
PROXY AND ATTORNEY-IN-FACT (WITH FULL POWER OF SUBSTITUTION) DURING THE TERM TO
VOTE OR ACT BY WRITTEN CONSENT, TO THE FULLEST EXTENT PERMITTED BY AND SUBJECT
TO APPLICABLE LAW, WITH RESPECT TO THE VOTING SHARES IN RESPECT OF ANY MATTER
SPECIFIED IN CLAUSE (i) OR (ii) OF

                                       2
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SECTION 2 HEREOF. THIS PROXY IS COUPLED WITH AN INTEREST AND SHALL BE
IRREVOCABLE THROUGHOUT THE TERM. THE STOCKHOLDER WILL TAKE SUCH FURTHER ACTION
AND EXECUTE SUCH OTHER INSTRUMENTS AS MAY BE NECESSARY TO EFFECTUATE THE INTENT
OF THIS PROXY AND HEREBY REVOKES ANY PROXY PREVIOUSLY GRANTED BY THE STOCKHOLDER
WITH RESPECT TO THE VOTING SHARES.

     SECTION 4.  Representations and Warranties. The Stockholder hereby
represents and warrants to the Trust and Merger Sub as follows:

     (a)  The Stockholder has all necessary power and authority to enter into
and perform its obligations under this Agreement and to consummate the
transactions contemplated hereby. This Agreement has been duly executed and
delivered by the Stockholder and constitutes a legal, valid and binding
obligation of the Stockholder, enforceable against the Stockholder in accordance
with the terms hereof.

     (b)  The execution and delivery by the Stockholder of this Agreement, the
performance by it of its obligations hereunder and the consummation by it of the
transactions contemplated hereby will not (i) conflict with, result in any
violation or breach of, or constitute a default under, any term or provision of
any note, bond, mortgage, indenture, lease, franchise, permit, license, contract
or other instrument or document to which the Stockholder is a party or by which
its properties or assets are bound or (ii) conflict with, or result in any
violation of, any law, ordinance, statute, rule or regulation of any
Governmental Entity or of any order, writ, injunction, judgment or decree of any
court, arbitrator or Governmental Authority applicable to the Stockholder or its
properties or assets.

     (c)  There is no requirement applicable to the Stockholder to obtain any
consent of, or to make or effect any declaration, filing or registration with,
any Governmental Entity for the valid execution and delivery by the Stockholder
of this Agreement, the due performance by it of its obligations hereunder or the
lawful consummation by it of the transactions contemplated hereby, except for
any filings required to be made by the Stockholder in connection with this
Agreement pursuant to Section 13(d) of the Exchange Act and the rules and
regulations promulgated thereunder.

     (d)  As of the date hereof, the Stockholder is the record and beneficial
owner of the number of Existing Shares set forth opposite the name of the
Stockholder on Exhibit A. The Existing Shares set forth opposite the name of the
               ---------
Stockholder on such exhibit are the only shares of capital stock or voting
securities of the Company of which the Stockholder is the record or beneficial
owner. Except as described on Exhibit A, the Shares are, or, if acquired after
                              ---------
the date hereof, will be, owned by the Stockholder free and clear of all liens,
claims, charges and encumbrances, except for those provided for under the
express terms of this Agreement and the Merger Agreement. The Stockholder has
not entered into any voting trust or other agreement with respect to any of the
Shares other than this Agreement and has not appointed or granted any proxy,
unless such appointment or grant is no longer effective, with respect to any of
the Shares.

                                       3
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     (e)  There is no suit, action, investigation or proceeding pending or, to
the knowledge of the Stockholder, threatened against the Stockholder at law or
in equity before or by any Governmental Entity that could impair the ability of
Stockholder to perform its obligations hereunder on a timely basis, and there is
no agreement, commitment or law to which Stockholder is subject that could
impair the ability of Stockholder to perform its obligations hereunder on a
timely basis.

     SECTION 5.  No Encumbrances on or Transfer of Shares. Except pursuant to
the terms of this Agreement or the Merger Agreement, for so long as this
Agreement remains in effect, the Stockholder shall not directly or indirectly
sell, convey or transfer record or beneficial ownership of any Shares by any
means whatsoever to any person, without the prior written consent of the Trust.
Without limiting the generality of the foregoing, for so long as this Agreement
remains in effect, the Stockholder shall not, directly or indirectly, (i) except
pursuant to the terms of this Agreement, grant any proxy or enter into any
voting trust or other agreement or arrangement with respect to the Shares or
(ii) except pursuant to the terms of the Merger Agreement, sell, assign,
transfer, encumber or otherwise dispose of, or enter into any contract, option
or other arrangement or understanding with respect to the direct or indirect
sale, assignment, transfer, encumbrance or other disposition of, any Shares, in
each case without the prior written consent of the Trust. If requested by the
Trust, the Stockholder shall cause an appropriate legend referring to the
restrictions provided for in this Section 5 to be placed on the certificates
evidencing the Shares.

     SECTION 6.  No Solicitation. For so long as this Agreement remains in
effect, and subject to Section 13 hereof, the Stockholder shall not, and shall
not permit any affiliates or, if applicable, any director, officer, employee,
consultant, agent, advisor or representative of Stockholder or any of
Stockholder's affiliates to, take or participate in any actions that, if taken
by the Company, would be prohibited under the terms of Section 4.2 of the Merger
Agreement.

     SECTION 7.  Additional Shares. For so long as this Agreement remains in
effect, the Stockholder shall notify the Trust and Merger Sub promptly of the
number of any additional shares of Company Common Stock and the number and type
of any other Shares acquired by Stockholder, if any, after the date hereof.

     SECTION 8.  Best Efforts. Each of the parties hereto shall use its
reasonable best efforts to take, or cause to be taken, all action and to do, or
cause to be done, all things necessary, proper or advisable under applicable
laws and regulations and which may be required under any agreements, contracts,
commitments, instruments, understandings, arrangements or restrictions of any
kind to which it is a party or by which it is or may be bound, in order to
effectuate the transactions contemplated by this Agreement, to obtain all
necessary waivers, consents and approvals from, and effect all necessary
registrations and filings with, any Governmental Entities, and to rectify any
event or circumstances which could impede the effectuation of the transactions
contemplated hereby.

     SECTION 9.  Governing Law. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of Delaware, without regard
to any principles of conflicts of laws that would result in the application of
the laws of any other jurisdiction.


                                       4
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     SECTION 10.  Severability. If any provision contained herein shall be held
to be invalid, illegal or unenforceable in any respect, the validity, legality
and enforceability of any such provision in every other respect and the
validity, legality and enforceability of the remaining provisions contained in
this Agreement shall not be in any way impaired thereby. Upon a determination
that any term or other provision is invalid, illegal or unenforceable, such term
or provision shall be modified, without any further action by any of the
parties, so as to effect the original intent of the parties as closely as
possible in order that the terms of this Agreement remain as originally
contemplated to the fullest extent possible.

     SECTION 11.  Expenses. All fees and expenses incurred by any of the parties
hereto in connection with this Agreement or any of the transactions contemplated
hereby shall be borne and paid solely by the party incurring such fees and
expenses.

     SECTION 12.  Further Assurances. The Stockholder shall execute and deliver,
or cause to be executed and delivered, at the expense of the Trust, all such
other and further documents and instruments and take all such further actions as
may be reasonably necessary in order to effectuate the transactions contemplated
by this Agreement.

     SECTION 13.  Action in Stockholder Capacity Only. It is expressly
understood and agreed that the Stockholder makes no agreement or understanding
under this Agreement in his or her capacity as a director or officer of Company.
The Stockholder is entering into this Agreement solely in his or her capacity as
a record and beneficial owner of Shares, and nothing contained herein shall
limit or affect, or impose any obligations with respect to, any actions taken by
the Stockholder in his or her capacity as a director or officer of Company.

     SECTION 14.  Termination. This Agreement shall terminate and be of no
further force or effect (i) by the written mutual consent of all the parties
hereto or (ii) automatically and without any required action by the parties on
the earliest of (A) the Effective Time of the Merger and (B) the date upon which
the Merger Agreement is terminated in accordance with the express provisions of
Section 7.1 thereof. The representations and warranties set forth in Section 4
hereof shall not survive the termination of this Agreement.

     SECTION 15.  Notices. All notices and other communications hereunder shall
be in writing and shall be given by delivery in person, by registered or
certified mail (return receipt requested and with postage prepaid thereon) or by
cable, telex or facsimile transmission to (i) in the case of the Trust or Merger
Sub, the addresses set forth in Section 8.2 of the Merger Agreement and (ii) in
the case of the Stockholder, the address set forth in Exhibit A hereto (or at
                                                      ---------
such other address as any party shall have furnished to the others in accordance
with the terms of this Section 15). All notices and other communications
hereunder that are addressed as provided in or pursuant to this Section 15 shall
be deemed duly and validly given (a) if delivered in person, upon delivery, (b)
if delivered by registered or certified mail (return receipt requested and with
postage paid thereon), 72 hours after being placed in a depository of the United
States mails and (c) if delivered by facsimile transmission, upon transmission
thereof and receipt of the appropriate answerback or confirmation.

                                       5
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     SECTION 16.  Amendment; Waiver. The terms and provisions of this Agreement
may be modified or amended only by a written instrument executed by each of the
parties hereto, and compliance with any term or provision hereof may be waived
only by a written instrument executed by each party entitled to the benefits of
the same. No failure to exercise any right, power or privilege hereunder shall
operate as a waiver thereof, nor shall any single or partial exercise thereof
preclude any other or further exercise thereof or the exercise of any other
right, power or privilege granted hereunder.

     SECTION 17.  Entire Agreement. This Agreement (including the Exhibit
hereto) constitutes the entire agreement among the parties with respect to the
subject matter hereof and supersedes all prior written or oral agreements and
understandings and all contemporaneous oral agreements and understandings among
the parties or any of them with respect to the subject matter hereof.

     SECTION 18.  Parties in Interest; Assignment. This Agreement shall be
binding upon and inure to the benefit of the parties hereto and their respective
successors and assigns (it being understood and agreed that nothing contained in
this Agreement is intended to confer any rights, benefits or remedies of any
kind or character on any other person under or by reason of this Agreement). No
party may delegate any of its obligations or assign or otherwise transfer any
its rights under this Agreement without the prior written consent of each of the
other parties. Any attempted or purported assignment, delegation or other
transfer by any party in violation of this Section 18 shall be null and void.

     SECTION 19.  Specific Performance. The parties hereto agree that
irreparable damage would occur in the event that any of the provisions of this
Agreement were not performed by the Stockholder in accordance with the terms
hereof. Accordingly, the parties agree that the Trust and Merger Sub shall be
entitled to injunctive relief to prevent breaches of the terms of this Agreement
and to specific performance of the terms hereof, in addition to any other remedy
now or hereafter available at law or in equity, or otherwise.

     SECTION 20.  Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

                                       6
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     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
duly executed as of the date first above written.


                                    PREMIER CONSTRUCTION PRODUCTS
                                    STATUTORY TRUST


                                    By:________________________________
                                       Name:
                                       Its Trustee:



                                    PREMIER CONSTRUCTION PRODUCTS
                                    ACQUISITION CORP.


                                    By:________________________________
                                       Name:
                                       Its:




                                    ___________________________________
                                    Name of Stockholder

                                       7
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                                                                       EXHIBIT A
                                                                       ---------

                                Existing Shares
                           Owned by the Stockholder


<TABLE>
<CAPTION>
                              Number of      Number of            Name and
Stockholder    Address         Shares     Shares Pledged     Address of Pledgee
-----------    -------         ------     --------------     ------------------
<S>            <C>            <C>         <C>                <C>
</TABLE>