At the beginning of the game you end up chasing balls. Once you get some of the slow, non-athletic kids knocked out, they line up behind the court & get the balls that miss.
And yes, the marching band pin shields were cannonball fodder. Of course. But they generally preferred that to being closer to the center line - they'd usually have enough time to only take it to the top of the head instead of the face.
Best was when the teams had thinned out & you could roll one ball like a bowling ball, and when it got close fire the remaining balls, machine-gun style, at the pin shield.