I have to admit, my first thought was of some of the threads on here where a parent says "my DC came home from school saying XYZ happened - aibu to report to offsted, the governors, the local newspaper...", and various people say "hang on a mo - have you double checked with the teacher that's what actually happened?" Then the poster gets the thread pulled "to protect her privacy."
Some teachers are bullies, yes, and if the events are as described then this teacher was being utterly shitty, but I'd be fascinated to hear the other side of the story, because the big caveat here is if the events are as described...
Additionally, as others have pointed out, involving the police was a massive over-reaction. And it's fascinating to know that there's no such thing as a stand alone offence of "hate crime" - it only exists as an aggravating factor in other crimes which would be crimes regardless. So, no, even if events were as described, this was not a hate crime.