G.B.
It truly sounds like he needs some anxiety meds to help him stay calmer. Working yourself up to this sort of high level makes the stomach acid churn even more.
I'd ask the school psychologist if he'd/she'd do some in class observations to see if kiddo is in need of help. It may be he's struggling with something at school and it's escalating to him becoming more dependent on you and therefore when you're not there he's in extreme distress.