I sat in the mezzanine on Saturday matinee and was in C-21, which was the "lottery" seats for that performance. I had seen the show twice prior, and the only things I couldn't see were the far upstage door to the classroom and the chalkboard - nothing too major honestly. Most of the action plays center, so you don't miss too much.
"Anybody that goes to the theater, I think we’re all misfits, so we ended up on stage or in the audience.” --- Patti LuPone.