(Bloomberg) -- Houghton Mifflin Harcourt Co., a publisher of education materials and research, is exploring a potential sale, according to people familiar with the matter.

The Boston-based company is working with an adviser, said the people, who asked not to be identified because they weren’t authorized to speak publicly. Private equity firms are exploring bids for the company, the people said. No final decision has been made and the company could opt to remain independent, they added.  

Houghton Mifflin rose 4.5% to close at $16.16 in New York on Friday, giving the company a market value of about $2.1 billion. The stock is up 329% in the past year. 

A representative for Houghton Mifflin declined to comment. 

Private equity firms have been acquiring education companies in recent years, as the industry grapples with technology shifts and other headwinds. Platinum Equity bought McGraw Hill last year for about $4.5 billion from Apollo Global Management Inc. A company backed by Francisco Partners called Renaissance Learning last year bought Nearpod. 

Houghton Mifflin, led by Chief Executive Officer John Lynch, offers schools programs including science, math and languages, to more than 50 million students in 150 countries, according to its website. 

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