I am actually a senior in high school right now. I've been wrestling since the beginning of middle school (sixth grade). For middle school, I always wore UnderArmor underneath, but once I entered high school, I found it more comfortable to just wear the singlet.
The singlets hid nothing, but honestly, it was no secret that I was hung. Even in middle school, I was bigger than the rest of the guys. Guys saw in the showers and weigh-ins and guys talk, so pretty much the school knew anyway.
I was teased, I got stares, I was given nicknames (Ryanaconda, Horsey, and I was notorious for being called The Hung One around the districts...one time at a competition, a guy from a competiting school and I were stretching still in our sweatpants and shirts, and I asked him if he knew who his competitor was and he answered, "The Hung One"). Honestly now, I don't care. I'm going to continue wrestling in college, I love it.