This was just last Tuesday. In my school gym the showers are all private and separated by a metal wall from the others next to it. But the wall just goes up to the height of the chest. The only kids who usually shower after gym class are these six guys who go in there to jerk off. They are all friends and they lean over the partition to look at each other.
A lot of us knew they were doing this and somebody must have told the gym teacher because on Tuesday, while they were at it, he went into the stalls area where he never goes and could see them looking over the partitions at each other, and could tell they were jerking for sure, and he told them to come right out of the showers and back into the locker room to dry off and get dressed.
They all, except one who had already cummed, had huge boners and had to walk back into the locker room hiding their boners behind a towel but they all really stuck out and everybody in the class saw them as they had to dry off and get dressed. The teacher stood there and watched them too, so everybody felt ok about staring at their hard cocks.
The story got around the whole school by lunch time and everybody knew who it was who got caught. But the teacher didn't make any big deal about it as I think he thought they were punished enough by being shamed that way.