Flinging acid in a tight classroom is fantasy. Say goodbye to your hands. Also got shot and spill it all over yourself.
Also, we have many large classrooms and lecture venues. Easily targeted.
Every argument against carry in the school, applies to religious institutions or malls. Crowded, confusion, panic, friendly fire, etc.
However, I support carry in all. I do strongly say I have no sympathy for those who want to carry and haven't taken the time to get a modicum of training as compared to just saying they 'would take him' out.