I'm also a teacher, so I completely get your dilemma. Both seasons have their ups and downs. Personally, I prefer Christmas. The weather is better (especially coming from up north) and there's just something about the Christmas decorations, especially at Magic Kingdom, that just make it that much more magical. Crowds will be bad either week. With attendance caps the way they are now, it's probably a negligible difference in crowds. When things go back to normal, then all bets are off and crowds will probably be worse at Christmas. However - IMHO, it's all about knowing what to expect and having a good plan to manage the crowds.