This is disgusting behavior. Those teachers should be sacked and forever barred from being in contact with any vulnerable population.
There were some bad teachers when I was in school. I was bullied by them, and I witnessed bullying and neglectful and even racist behavior of these same teachers toward my classmates and friends. This wasn't subtle either. It was quite overt, but everyone just assumed "that's the way it is." It wasn't a special education environment either, but mainstream--and I can only imagine how awful it is being vulnerable in an isolated classroom environment.
I experienced and witnessed students being sworn at, a student being made fun of for his race, a friend of mine being called a liar and punished for a bullying situation involving another student, students being reduced to tears while teachers berated them. My friend was even struck by a teacher in kindergarten for having untied shoes. Looking back, it was unbelievable that anyone learned anything.