I assume an injured player situation is handled the same in NCAA and High School. I handle it as follows during high school games:

If a player is injured and in danger of being injured further or injuring another I will stop play immediately. If the player is unconscious I will stop the play immediately no matter how the play is developing. If the play is heading to the basket I will let it play until a basket is made or the ball settles in one position.

This is how I have been taught to deal with injured players in high school games. However, I have found that dealing with injured players it is best to use common sense and if you stop a play to protect a player most coaches aren't going to get to upset.