With each passing year they will gain more body strength and each coach can encourage them to raise their starting point on their shot release. The body and proportionate strength grow in progressive stages and so does the shot. There are some young kids who can execute a technically perfect shot at that age, but in most cases the active legs and explosive strength is sorely lacking. Focus on improving the technique surrounding the shot preparation and set up which is more critical to developing into a great shooter at this stage. Secondly, you can use examples of pro and college players as motivation.
Kids are smart and they watch what others do.
As they grow and they begin to miss shots because of shooting the ball too low, or from the wrong position, they will be highly motivated to change and grow. In the meantime get them focused on their footwork, and being more prepared to shoot quickly. In most cases the lower body technique and shot preparation skills are so ingrained in their motor skill library they end up frustrated and underachieve as shooters. Be patient with their strength growth and encourage them by using other examples. The Basketball Highway .