There is no CYO in Evansville. Down here, the only HS that has a league with teams affiliated with feeder school is Memorial. The feeders often pair up to get enough numbers since so many kids play the devil's games (soccer and fall ball).
Central, North, GS, HH and Castle all have youth leagues (not necessarily run by the HS, but with varying degrees of input from the HS coach). Most of the MD and Reitz younglings play in a westside league. There is also a league on the eastside. Our teams play against some of the other leagues from time to time to get some variety in the scheduling. I know nothing about the number of teams or roster sizes in those leagues though.