Besides the cons that have already been mentioned, I would be afraid that one of the students would feed him something he shouldn’t be eating – either out of ignorance of a proper rabbit’s diet, or because the student thought it would be funny or cool to give your bunny a piece of a candy bar or gum or anything that could be harmful. You mentioned even letting your bunny run around. With students walking about, the bunny could get a paw stepped on or he could get underfoot and trip up someone. My bunnies are bad about that.
The Sanctuary where I volunteer has taken in some classroom rabbits over the years, and I realize this is a different situation – you are the rabbit parent and not a teacher who will be looking to get rid of a rabbit when the school year ends or when the rabbit displays bad behavior toward the students, such as nipping them (which they likely deserved). All the classroom rabbits we have taken were in poor health – one was fed French fries and other stuff from student’s lunches, plus he never was treated for skin mites. Another was aggressive from being grabbed at by students, and she had an eye condition and a heart condition that was never treated. There were others, and none showed up in good shape, so I automatically have negative thoughts when I hear about classroom rabbits. I want to repeat that I know the situation is different here, since you are talking about your much loved rabbit. But I know that most rabbits are homebodies and that they will likely be far happier in their own home environment, plus the fact that accidents could happen and I don’t think a classroom is a good place for what can be a fragile animal.