Ran into an interpretation of the "tuck" rule I am not familiar with.

[hoopguy]

Our rules interpreter asked us to basically do what your ref did in your game. However, I believe it was very rarely done in varsity games. AAU is a good place for this to occur in that it rarely matters the outcome of the game but it serves as a good lesson for the kid. I doubt if he will allow his shirt to be untucked if he thinks it will get him sent out of the game which is the whole purpose for the action.