Leaning over the plate

[Rufus]

I coach a 12U travel team and we had a situation during a scrimmage this weekend. The batter's feet were in the batter's box, but his upper body leaned over the plate. I wasn't aware of this during the game but some of my parents let me know about afterward.

I saw in NFHS 7-3-5a says that a batter may not lean over home plate, and I could probably find the same rule in OBR, but my question is this:

I want to instruct my pitcher and/or catcher to make the umpire aware of the situation in a respectful manner that addresses the problem. I realize that umpires will usually deal with this when they see but, if they don't or are not inclined to, what is the best way for my players to address the issue?

Thanks in advance.