"The problem is that what is high spirits to some children can appear to be bullying to others."
HERE'S THE PROBLEM!!!
High spirits????? are they shittin' me?
If he were my son(and I have a 13 yr. old son) I would have pulled him out of school...found each and every kid that picked on him and paid a bigger, older kid to kick their asses and make it known that anyone else bullying would get more of the same. Then I would have went to speak to their parents...door to door...I would have pressed charges against the school and just for fun,went to school daily to give the evil eye to any little shit ballsy enough to step out of line....
naw...i'm not a hot head.
I bet that girl teasing him was the worst part. Though it was all really bad.