There are SOME high school wrestlers who are so fit and muscular you'd never know they were just teenagers.However a 15 year old is highly unlikely to be in THAT group. I have certainly seen high school athletes 17 and 18 that have impressive physiques.
I was pretty sexually active from the time I was 14, and I was fucking a 17 year old, so I am not really of the opinion that teenagers are somehow always naive and innocent about sex.
Doesn't give adults permission to be pursue relations with teenagers, but I do feel that people are quick to assume that all these relationships are always predatory by the adult.
My cousin was sleeping with a 32 year old high school teacher when she was 17. She has always defended that as HER decision and that SHE pursued HIM, not the other way around.