SECOND AMENDMENT TO THE RIGHTS AGREEMENT

Exhibit 4.1

EXECUTION COPY

SECOND AMENDMENT TO THE RIGHTS AGREEMENT

THIS SECOND AMENDMENT TO THE RIGHTS AGREEMENT (this “Amendment”) is made and entered into as of the 25^th day of April, 2007, between Pediatric Services of America, Inc., a Delaware corporation (the “Company”), and Mellon Investor Services LLC (formerly ChaseMellon Shareholder Services, LLC), a New Jersey limited liability company, as Rights Agent (the “Rights Agent”). Capitalized terms used herein and not otherwise defined have the meanings ascribed to such terms in the Rights Agreement (as defined below).

WHEREAS, the Company and the Rights Agent entered into the Rights Agreement, dated as of September 22, 1998, as amended (the “Rights Agreement”), setting forth the terms of the Rights (as defined therein);

WHEREAS, the Company and the Rights Agent may, from time to time, supplement or amend the Rights Agreement pursuant to the provisions of Section 27 of the Rights Agreement;

WHEREAS, the Board of Directors of the Company (the “Board of Directors”), on April 25, 2007, resolved that the Agreement and Plan of Merger, dated as of April 25, 2007, among Portfolio Logic LLC, Pointer Acquisition Co., Inc. and the Company (the “Merger Agreement”), and the Merger (as defined in the Merger Agreement), are fair to and in the best interests of the Company and its stockholders;

WHEREAS, in connection with the execution and delivery of the Merger Agreement, the Company also desires to provide for the potential participation in the transactions contemplated by the Merger Agreement by the “D3 Parties” (as defined below);

WHEREAS, in connection with the above, the Company desires to amend the Rights Agreement;

NOW, THEREFORE, in consideration of the premises and mutual agreements contained herein, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Company and the Rights Agent hereby agree as follows:

SECTION 1. Amendment to Rights Agreement. The Rights Agreement is hereby amended as follows:

(a) The definition of “Acquiring Person” in Section 1(a) of the Rights Agreement is amended by inserting the following text at the end of such definition:

“Notwithstanding anything in this Section 1(a) to the contrary, none of

(i) Portfolio Logic LLC, a Delaware limited liability company (“Parent”), Pointer Acquisition Co., Inc., a Delaware corporation (“Merger Sub”), or any of their Affiliates, Associates or stockholders, or the general partners, limited partners or members of such stockholders, or

(ii) David Nierenberg, The D3 Family Fund, L.P., a Washington State limited partnership, The DIII Offshore Fund, L.P., a Bahamas limited partnership, The D3

Family Bulldog Fund, L.P., a Washington State limited partnership, Nierenberg Investment Management Company, a Washington State corporation, Nierenberg Investment Management Offshore, Inc., a Bahamas corporation, and the shareholders, general partners, directors and officers of any of the foregoing (collectively, the “D3 Parties,” and, together with the Persons enumerated in clause (i) above, the “Exempted Persons”)

either individually, collectively or in any combination, shall be or be deemed to be an “Acquiring Person” by virtue of or as a result of (A) any agreements, arrangements or understandings (whether or not in writing and including, but not limited to, agreements, arrangements or understandings with respect to acquiring, voting, holding or disposing of shares of Common Stock) among all or any of the Exempted Persons in connection with the Merger Agreement or the Merger, (B) the execution and delivery of the Merger Agreement or (C) the conversion of Company Common Stock into the right to receive the Merger Consideration pursuant to the Merger Agreement or the consummation of the Merger (the transactions described in clauses (A), (B) and (C), as well as those referred to in the next paragraph, being the “Exempted Transactions”).

Without limiting the generality of the preceding paragraph, none of the following activities by any one or more of the D3 Parties shall affect or impair the status of the D3 Parties as a Special Acquiring Person under the definition of “Acquiring Person” in this Section 1(a) and all of such activities shall constitute Exempted Transactions: (i) discussing and negotiating with any other Exempted Person, including its Affiliates, Associates, general partners, limited partners, members, advisors or potential financing sources, the possible participation (through equity investment or contribution of shares of Common Stock, as well as a possible agreement to vote their shares of Common Stock in favor of adoption of the Merger Agreement and possible participation in the governance of the Company following the Merger) of any of the D3 Parties in the Merger; (ii) reaching any agreement, arrangement or understanding (whether or not in writing and including, but not limited to, agreements, arrangements or understandings with respect to acquiring, voting, holding or disposing of shares of Common Stock) with any other Exempted Person regarding such possible participation; (iii) if any such agreement, arrangement or understanding is reached, effectuating the same; and (iv) making any public announcement or filing with the Securities and Exchange Commission (the “SEC”) with respect to any Exempted Transaction.”

(b) Section 1 of the Rights Agreement is amended by inserting the following subsections at the end of such Section 1:

“(ff) “Merger” shall have the meaning set forth in the Merger Agreement.

“(gg) “Merger Agreement” shall mean the Agreement and Plan of Merger, dated as of April 25, 2007 by and among Parent, Merger Sub and the Company.

“(hh) “Merger Consideration” shall have the meaning set forth in the Merger Agreement.”

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(c) The definition of “Expiration Date” in Section 1(o) of the Rights Agreement is amended and restated to read as follows:

“(o) “Expiration Date” shall mean the earliest of (i) the time at which the Rights are redeemed as provided in Section 23 hereof, (ii) the “Final Expiration Date” (as hereinafter defined in this section), or (iii) immediately prior to the Effective Time (as defined in the Merger Agreement), but only if the Effective Time shall occur.” The Company shall promptly provide the Rights Agent with written notice with the Effective Time but any delay or failure in the giving of such notice shall not affect the occurrence of the Expiration Date. The Rights Agent shall be deemed to have no knowledge of the Effective Time until such notice is received.

(d) The definition of “Stock Acquisition Date” in Section 1(z) of the Rights Agreement is amended by inserting the following sentence at the end of such definition:

“Notwithstanding anything in this Section 1(z) to the contrary, a “Stock Acquisition Date” shall not be deemed to have occurred solely by virtue of or as a result of any Exempted Transaction or the public announcement thereof (including in an SEC filing).”

(e) The definition of “Triggering Event” in Section 1(ee) of the Rights Agreement is amended by inserting the following sentence at the end of such definition:

“Notwithstanding anything in this Section 1(ee) to the contrary, a “Triggering Event” shall not be deemed to have occurred solely by virtue of or as a result of any Exempted Transaction or the public announcement thereof (including in an SEC filing).”

(f) Section 3(a) of the Rights Agreement is amended by inserting the following sentence at the end of such Section 3(a):

“Notwithstanding anything in this Agreement to the contrary, a “Distribution Date” shall not be deemed to have occurred solely by virtue of or as a result of any Exempted Transaction or the public announcement thereof (including in an SEC filing).”

(g) Section 25(b) of the Rights Agreement is amended by inserting the following sentence at the end of such Section 25(b):

“Notwithstanding anything in this Agreement to the contrary, the Company shall not be required to give any such notice in connection with any Exempted Transactions.”

SECTION 2. Full Force and Effect. As herein modified, the Rights Agreement shall remain in full force and effect and is hereby ratified and confirmed. In executing and delivering this Amendment, the Rights Agent shall be entitled to all of the privileges and immunities afforded to the Rights Agent under the terms and conditions of the Rights Agreement.

SECTION 3. Counterparts. This Amendment may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. Delivery of an

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executed counterpart of a signature page to this Amendment by telecopier shall be as effective as delivery of a manually executed counterpart of this Amendment.

SECTION 4. Governing Law. This Amendment shall be deemed to be a contract made under the laws of the State of Delaware and for all purposes shall be governed by and construed in accordance with the laws of such State applicable to contracts to be made and to be performed entirely within such State.

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

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