How can I stop sweating?!?

Kso, My school is having a spring concert and since Im in the band I have to wear a white blouse and black pants. But , I always sweat at school! Its sooo annoying! When I get home I seriously NEVER swet..Its just at school. So can you give me any tips to not sweating or somthing. && Im a 12 year old girl :) KThanks <3