Sometimes they trip on their own egos. And getting those big heads through doors might pose a problem.
The dangers that I'm aware of are the damages done to the students by the teachers. I still carry the scars of being ridiculed by two teachers who thought it was funny to pretend to not hear me even when I talked in almost a scream because I was so horribly shy (from abuse at home). I had a male teacher in 5th grade who allowed all the boys in my class to throw basketballs at me as hard as they could while I was made to stand up against the wall outside the school. He stood there and laughed. I was overweight, wore horrible clothes from the Salvation Army, and had zero self-esteem. The teachers who were cruel (and believe me, in the 60's there were plenty) saw kids like me as easy prey. I have so many stories I could tell about what was done to me and to other classmates, it's horrible. So abuse at school and abuse at home....what a great life.