...at 12U a 32 mph changeup is hitting the dirt.
I know when we did machine pitch in rec a few years ago for some games or portion of games (think it was technically 10u, but most girls were 7-8-9), we set machine at 35, pitch had virtually no arc to it (did tend downwards a bit, but not on arc, down drom beginning). Seems these pitchers changeup at 12u is more in the high 30s/low 40s, so it is not inevitable it hits the dirt