NEW YORK (AP) — Educational content maker McGraw-Hill Education plans to go public.

Best known as a publisher of textbooks and instructional materials, the company is now investing heavily in developing digital content and technology like its "Reading Wonders" and "Economics: Principles, Problems, and Policies" programs.

It filed for an IPO that was valued at up to $100 million, according to a form filed Friday with the Securities and Exchange Commission.

The New York-based company says its programs are used by 250,000 higher education instructors and in 13,000 school kindergarten- to 12th-grade school districts. It also makes products for companies, academic institutions, libraries and hospitals.

The company reported $2.03 billion in adjusted revenue in 2014, and said 38 percent of revenue from its higher education business, its largest, came from digital materials. That's up from 15 percent in 2010. Digital revenue accounted for only 21 percent of its K-12 revenue.

McGraw-Hill Education lost $330.7 million last year as it invested $150 million in digital learning, and plans to spend another $175 million on those programs in 2015.

The $100 million price tag is an estimate used for the purpose of calculating a filing fee. McGraw-Hill Education wants to list its shares under the symbol "MHED."

Apollo Global Management bought McGraw-Hill Education from what was then The McGraw-Hill Cos. The $2.3 billion deal closed in March 2013, and the rest of McGraw-Hill is now McGraw Hill Financial Inc., a company focused on serving the global capital and commodity markets.

Apollo Global will continue to hold most of the voting power in the company after the IPO.