((((((((xylia)))))))))))
Memories are sometimes difficult to deal with. It sounds like some PTSD grabbed hold of you and put you back into that familiar rotten place.
Maybe if you could try some grounding before you walk into the school and while you are there? Some deep breathing to calm the heart rate and slow it down. Will also help you to gain a bit of brain control too. If sitting at your desk, make sure you feet are planted firmly on the floor in front of you. Take notice of the people in the room, the colors of their clothing, make mental notes of where you are and that it is not the place where you have been in the past. Talking calmly to yourself (which I know is easier said then done) to come back around to the present may help as well.
I wish you well and hope the days go by more smoothly for you.

sabby