An American private-equity company is acquiring TSL Education, Ltd., giving the buyer purview over a community spanning millions of educators and students—including members of the United States’ second-largest teachers’ union, through a platform that allows teachers to share resources with one another.

Access to an estimated 52 million teachers and students is said to be one reason U.S.-based TPG Capital, LLP is purchasing TSL. The London-based company publishes TES (the Times Educational Supplement), and owns the TES Connect website, which it says is the largest network of teachers in the world—as well as Share My Lesson, the American Federation of Teachers-sponsored platform for teachers who want to post and exchange lessons and information online. Although the official price in the sale was not disclosed, a story from Reuters indicates that the transaction is valued at close to $600 million.

Janet Bass, a spokeswoman for the 1.5 million-member AFT, yesterday said that under Share My Lesson’s partnership with TES Connect—on which it is patterned—the AFT-based platform will continue to be a free resource for teachers, by teachers.

“For now, Share My Lesson will remain as it is and only get stronger,” she said. “We have full contingency plans that will allow AFT to take over full ownership of Share My Lesson, or find another partner” under specific circumstances, Bass said. “Whatever partner we have, has to be comfortable working with a union—because that’s who we are—and share our value and our commitment to providing teachers with high-quality resources.”

Since its inception one year ago, Share My Lesson has had 2.8 million downloads, and serves educators abroad, like those who teach at U.S. Department of Defense schools, Bass said. TES Connect, its U.K.-based counterpart, reports that it has 3.6 million downloads a week globally, according to the company’s website.

Karl Peterson, TPG Capital’s managing partner, in a statement, described the rationale behind the company’s purchase as follows: “TSL is well known for its longstanding and vital role in the UK education sector…TPG’s global presence and extensive online experience fit well with the company’s ambitions and we anticipate accelerating growth through further investments in TSL’s digital capabilities.”

A co-founder and former CEO of the discount travel website Hotwire, Peterson’s background in building online communities dovetails with the opportunity to grow the reach of the TSL Education properties in the world of education, experts say.

Education Week asked TSL Education to provide a geographic distribution of the 52 million teachers and students, identifying how many are in Europe, the U.S., and other regions of the world. A spokeswoman for the company indicated that TES Connect has 2.7 million registered members, and Share My Lesson–which launched a year ago–has 280,000 subscribers. The company has not yet provided Education Week with any additional details on its global reach.

The Independent reports that this is the third ownership change in eight years for TSL. Charterhouse, a British-based private equity firm that has owned the property since 2007, is the seller. The TSL Education announcement on Monday, July 8 indicated that TPG will close on the purchase in the third quarter of 2013.