Why are teachers so cruel?

I'm stuck in psychology at school, because there aren't any other subjects I can go into.

I recently missed an important SAC because I had to have a meeting with a group of counsellors and therapists about being on suicide watch.

My psych teacher has been really rude to me since and is always really harsh towards me when I talk to her.

Oh, I'm sorry that I wanted to die Mrs Watson, it's so rude of me to not think about my grades when my depression is trying to kill me.
You're absolutely right, it's unacceptable of me to sleek help and stop trying to kill myself.
Because, obviously, GRADES ARE MORE IMPORTANT THAN MY LIFE.