There's an article on the Philadelphia Inquirer website now with more details, although I don't think it's available without a subscription. Apparently, the objections were language, although there is a warning about strong language on the theater company's website and the theater says they had conversations with the schools beforehand. One of the groups left at intermission but the other, which was 5th graders, were led out from the front row in the middle of the show.
Sounds like the schools messed up here. If they don't like the content, they should have asked the right questions beforehand.