Apollo agreed in 2012 to buy the education unit of McGraw-Hill Cos. for about $2.5 billion, including debt. After the sale was completed, the remaining parent company changed its name to McGraw Hill Financial Inc., later changing it again to

S&P Global Inc.

The Apollo-owned company retained the McGraw Hill name.

McGraw Hill provides textbooks and digital-learning tools and platforms for higher education, grade-school districts and a variety of other academic institutions and companies. Its products are distributed in more than 100 countries around the world.

The company became less print-centric under Apollo’s ownership, completing six acquisitions of digitally focused companies since 2013. It now brings in $1 billion in annual revenue from digital, accounting for more than 60% of its top line, compared with less than 25% in 2013.

Last year, McGraw Hill agreed to terminate a merger with rival educational publisher Cengage after the companies determined that divestitures required by regulators to grant approval for the deal would make it uneconomical.

Apollo, which manages more than $460 billion across credit, private equity and real estate, specializes in buying companies that are down on their luck and returning them to growth. Last month, it announced a deal to buy

Verizon Media,

the unit that owns Yahoo and AOL, from

Verizon Communications Inc.

for about $5 billion.

Los Angeles-based Platinum Equity manages more than $25 billion and has a portfolio of about 40 companies around the world. Founded in 1995 by

Tom Gores,

it buys businesses across a variety of sectors, including manufacturing, transportation and logistics, media and entertainment and technology, among others.

Write to Miriam Gottfried at Miriam.Gottfried@wsj.com