One player underhand passes the ball high to themself and then underhand passes the ball back to their partner.
Everytime a player digs or underhand passes the ball it is important they bent their knees before their arms make contact with the ball.
Why coach this drill? Because passing over the head improves coordination and reaction time.
Too easy? Introduce additional tasks between the underhand passes such as a 360 degree spin or hand claps.
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.