You can play with them and love them before going to work and after you return home. Bunnies have sensitive ears and, no matter how quiet kids are, there will always be noise in a classroom and a teacher talking most of the time when the bunnies are supposed to be quiet and sleeping. Bunnies like to chew on anything they find. Even knowledgeable rabbit caregivers have had this happen accidentally in their homes, so imagine the chances of a bunny encountering these dangerous items with lots of kids around. The potential risk is multiplied by the number of children in the classroom.
Bunnies have very sensitive respiratory systems.
Many things can happen when you leave the bunnies unattended. There are cruel people everywhere. You must have heard about the Noah's Ark case, wherein children from the neighborhood broke into a shelter and killed 21 cats and injured many more. You might not have heard of an HRS educator in Miami who had her fosters in a house she was building and a neighborhood kid broke into it and stole all her foster bunnies. She was lucky that the media picked up on the story.