Batter remaining in box after pitch.....

Help please!!!!
There seems to be some confusion in our league. I coach a boys 10 to 12 minors team. The issue is whether or not the batter should/can remain in the batter's box after the pitch (especially if the ball gets by the catcher).

Twice last week this issue came up. The first time the catcher couldn't make the throw to 2nd because the batter was in the way (the ball was right behind his foot). I thought that this should have been interference (7.11) but was ruled against by the umpire.

The second time was a near disaster. The catcher again missed the pitch and jumped up to chase it down, throwing off the mask in the process. The batter (a lefty) never moved. The catcher fielded the ball in the area behind the batter. As the catcher threw the ball back to the pitcher, the batter took a practice swing (yes, while still in the box). The bat struck the catcher in the side of the mouth, chipping a tooth. Thankfully, it is a baby tooth and there is no permanent damage.

Please share your thoughts and feedback!