It is a sad day that we need to be wary of these things with our children.
It may be totally innocent, but how do you or I know that?
As parents it's our job to protect our children, if something concerns us we should follow up on it, because if we don't and something bad happens as a result we'd never forgive ourselves.
The solution could be as easy as making sure a teacher is in the change rooms with the kids. It doesn't have to be a big deal with accusations, it's just about ensuring the safety of our children.