I always go to great lengths to avoid talking to people I knew in high school
That sounds like a big effort. Did you have a lot of bad memories from high school?
There was an incident with a math teacher and I don't want to remember it.
High school can be difficult for many people but it is not good to avoid people even if you have bad memories. We encounter people we know everywhere and it is better to be polite and move on.
The hell with all these people.
Definitely high school sucks, but its something we all have to live through. But I believe it would be a nice idea to open up to some people, at least a teach, counselor, or a librarian. It's still a very healthy idea to interact with others!