Since the late 1990s, reformers around the country have been breaking up large, anonymous “comprehensive” high schools in favor of smaller institutions. While big schools offer students a bewildering array of classes, language options and after-school activities, the small academies offer fewer, tightly focused classes organized around a school’s central theme. Last year New York City opened 29 academies, including ones that focus on maritime culture, great books, law and health care. Schools Chancellor Joel Klein says the Gates gift, which will be funneled through seven nonprofit groups, will create 200 more such schools.

But breaking up is hard to do. In order for small academies to succeed and be cost-effective, many faculty members must agree to act as both teachers and administrators in the course of a school day. Is the ossified New York public-school system ready for that? Paul Hill, head of the Center on Reinventing Public Education, has studied small academies around the country. He says he isn’t overly optimistic about creating them in New York. “You can find examples where this has succeeded,” says Hill. “But transforming big schools into little ones is complicated. Many will fail. It’s not easy to fix a high school.” Even if you’re a billionaire like Gates.