do yall wear shirts under jumpers?

Hiya, so its summer for me now and bruh its so freakin hot. I found out some people don't wear shirts under their jumpers. Thinking this would help solve the problem of feeling like im in a sauna for 6 hours straight (school). And i gotta keep that jumper on to cover my arms - got fresh wounds on them rn. So, is this not-wearing-a-shirt-under-a-jumper thing a normal?