Starting from stage 1, the child gives a service and tries to get it over the net. If the child is successful he will move to stage 2, if not the child will keep trying until eventually will get the ball over the net.
New hitters rarely miss because of their arm. They miss because of their feet. Build a reliable approach, then time it with your setter.
When your hitter gets stuffed, five teammates standing and watching is how you lose the point. Good attack coverage turns a blocked ball into a second swing.
Coaches spend hours correcting arms in serve receive when the real fault is almost always the feet. Fix the movement and the platform fixes itself.