With kids back in the classrooms, parents and teachers have been complaining about overcrowding. According to the UFT, the number of jam-packed classes has increased by 20 percent this year. Many students end up sharing books, while others are made to learn inside converted closets. "It's like on the subway at rush hour," said Erin Flanagan, a P.E. teacher in Flushing, "when the doors open, there's no room. That's what the hallways are like."