It happens occasionally, like once a year. Usually its a kid wandering around and goes below the free throw line or it talking to his/hercoach (if you werent paying attention to tell them to move) below the line. Think I have only called a kid once for breaking the arc in a HS game.

You coach them in this situation?

If I see a player below the free throw line extended before a free throw, I'll tell him to back up. Even while the ball is at the disposal of the player, if a player wanders and wants to have a word with the coach but in doing so will be below the free throw line extended, I'll remind the coach about it since I'm right there.

I had a player do the following after the ball was at the disposal of the free throw shooter: Leave the 3rd lane space opposite table and go outside the arc, and then return to that space. Fortunately, we were not near a 10 second violation by the shooter who was taking her time. But, I would have had disconcertion or a violation on the happy wanderer long before I reached 10. Or 9 1/2 even.

Interesting. In a high school game (JV and above), I just call this if I see it.

+1

Violation or delayed violation as soon as it happens.

If its before the ball is given to the thrower, get 'em up. If not, well too bad and here comes the violation/delayed violation.

For some reason, this is one where I don't do much preventative officiating. I don't rush the ball to the shooter to play gotcha, but I'm not getting them into position either. I probably should, but I don't.

After they get through middle school, they ought to know this one.