Same formation, 5-7 yards between players, one ball per trio. A serves underhand lob to B who heads to C. C serves A who heads to B, and so on. Emphasize moving entire body to enable powerful headers struck with forehead. Groups of four with two balls, players in a diamond with approx. 5 yards between players.
Next lob comes immediately.
This results in the working player having to deal with balls from a variety of angles, identify a target, and perform header. As players improve, increase distance and allow non-working players to move around. Working players set up in center of area. Run for a minute and then have players switch roles. Object is to move down field and score on header.