Have players form two lines under a basket. Roll a ball out right between the two lines. On your command the first player in each line hustles after the loose basketball. Have three players spread out all facing the basket about 15' away from the hoop.
Coach shoots a ball and all players crash the boards for the rebound.
The player who comes down with the ball tries to score against the other two, one shot only. As the coach you want to call only fouls where there is a serious chance of a player getting hurt. The idea is for them to be agressive and really go after it so don't plan on calling fouls. I've never heard of a kid getting really hurt in this drill. If the ball goes in shoot it again.