Hands in his pants

Both my girls take gymnastic class together once a week, there are a few boys in the class, one I have named "Hands in his pants Evan". Every week he has his hands down the back side of his pants, under the underwear showing some butt crack and it really grosses me out!

Once he pulled his hands out of his pants and patted Amelia on the head, yuck, yuck, yuck!!!! I just think of all the rings, bars, floor mats he touches and then all the other kids touch. Needless to say as soon as we walk in the door it's wash your hands.

His mom, who is usually reading a book, has seen him do this and once I even brought it to her attention by nicely saying I think Evan has an underwear problem. She said she didn't want to embarrass him and went on reading. Last week she did see him and did go tell him to stop, which lasted all of 5 minutes. And this week... hands down the pants again and again and again!!! What is the deal? The teacher has also told him several times to stop. As a mom I would be having a talk with my child, hands in your pants and you come out of class, that's it. Am I over reacting?