That sounds like a frightening situation, V., and I don't understand why the administration would allow someone like that in the school. At the root of it, I would suspect an abusive/neglectful home situation and/or sensory or developmental issues.
Tongue in cheek humor can mask a lot of buried pain and shame.
The bicycle is the most civilized conveyance known to man. Other forms of transport grow daily more nightmarish. Only the bicycle remains pure in heart. ~Iris Murdoch, The Red and the Green