This Amendment No. 4 (this “Amendment”) amends and supplements the Tender Offer
Statement on Schedule TO filed with the U.S. Securities and Exchange Commission on March 7, 2022 (together with any amendments and supplements hereto, this “Schedule TO”) by Harbor Purchaser Inc., a Delaware corporation (the
“Offeror”) and a wholly owned subsidiary of Harbor Holding Corp., a Delaware corporation (“Parent”), which is an indirect, wholly owned subsidiary of The Veritas Capital Fund VII, L.P., a Delaware limited
partnership (the “Sponsor”). This Schedule TO relates to the offer by the Offeror to purchase all of the issued and outstanding Company Shares at a purchase price of $21.00 per share (the “Offer Price”), net to the
holder thereof in cash, net of applicable withholding taxes and without interest, upon the terms and subject to the conditions set forth in the Offer to Purchase, dated March 7, 2022 (the “Offer to Purchase”), and in the
related Letter of Transmittal (the “Letter of Transmittal”, which, together with the Offer to Purchase, as each may be amended or supplemented from time to time in accordance with the Merger Agreement described below, collectively
constitute the “Offer”), copies of which are annexed to and filed with the Schedule TO as Exhibits (a)(1)(A) and (a)(1)(B), respectively. All the information set forth in the Offer to Purchase is incorporated herein by reference in
response to all of the applicable items in the Schedule TO and is supplemented by the information specifically provided in the Schedule TO, except that such information is amended and supplemented to the extent specifically provided in this
Amendment. The Agreement and Plan of Merger, dated as of February 21, 2022 (as amended by Amendment No. 1, entered into on March 21, 2022, a copy of which is attached as Exhibit (d)(5) to the Schedule TO), by and among Parent, the
Offeror and Houghton Mifflin Harcourt Company, a Delaware corporation (“HMH”), a copy of which is attached as Exhibit (d)(1) thereto, is incorporated herein by reference with respect to Items 4 through 11 of the Schedule TO. Unless
otherwise indicated, references to sections in this Amendment are references to sections of the Offer to Purchase. Capitalized terms used and not otherwise defined in this Amendment shall have the meanings assigned to such terms in the Offer to
Purchase or in the Schedule TO. This Amendment is being filed to amend and supplement Items 1 through 9 and Item 11 of the Schedule TO as reflected below.
ITEMS 1 THROUGH 9 AND ITEM 11.
The Offer to Purchase
and Items 1 through 9 and 11 of the Schedule TO, to the extent such Items incorporate by reference the information contained in the Offer to Purchase, are hereby amended and supplemented by adding the following text thereto:
“The Offer and withdrawal rights expired as scheduled at one minute after 11:59 p.m., New York City time, on April 6, 2022 (the “Expiration
Time”). The Depositary and Paying Agent has advised Parent and Offeror that, as of the Expiration Time, a total of 72,926,195 Company Shares (excluding Company Shares with respect to which notices of guaranteed delivery were delivered) were
validly tendered and not properly withdrawn pursuant to the Offer, representing approximately 56.5% of the Company Shares outstanding as of the Expiration Time. In addition, the Depositary and Paying Agent has advised Parent and Offeror that, as of
the Expiration Time, notices of guaranteed delivery had been delivered with respect to 2,184,308 additional Company Shares, representing approximately 1.7% of the outstanding Company Shares as of the Expiration Time.
As of the Expiration Time, the number of Company Shares validly tendered and not properly withdrawn pursuant to the Offer satisfied the Minimum Condition, and
all other conditions to the Offer were satisfied or waived. Accordingly, Offeror has accepted for payment all Company Shares validly tendered and not properly withdrawn pursuant to the Offer and will promptly pay for all such Company Shares in
accordance with the terms of the Offer.
As a result of its acceptance for payment of the Company Shares validly tendered and not properly withdrawn
pursuant to the Offer and in accordance with Section 251(h) of the DGCL, Offeror owns at least the percentage of Company Shares that would be required to adopt the Merger Agreement without a vote of the stockholders of HMH. Accordingly, Parent
and Offeror expect to complete the acquisition of HMH on April 7, 2022 by consummating the Merger pursuant to the Merger Agreement without a vote of HMH’s stockholders in accordance with Section 251(h) of the DGCL. At the Effective
Time, all remaining outstanding Company Shares not accepted for payment in the Offer (other than any (i) Company Shares owned by HMH or any of its wholly owned subsidiaries (including Company Shares held as treasury stock), or owned by Parent
or any of its wholly owned subsidiaries, including the Offeror, in each case, immediately prior to the Effective Time and (ii) Company Shares owned by any stockholders who have properly exercised their appraisal rights under Section 262 of
the DGCL) that are outstanding immediately prior to the Effective Time shall be cancelled, shall cease to exist, shall no longer be outstanding, and shall be automatically converted into the right to receive $21.00 in cash, without interest.