These teams have finished in the top four of their respective IHSA state tournament:[4] The school was initially known for its football team, which made 8 appearances in Chicago's Prep Bowl, which pitted the champion of the Catholic League against the winner from the Chicago Public League from 1934 to 1956.

In particular, the 1937 and 1941 Prep Bowls are recognized as holding the state of Illinois' all-time records for attendance at a football game.

The 1937 attendance was estimated at 110,000 spectators, which saw Leo lose to Austin High School, 26–0.

The 1941 game saw 95,000 spectators watch Leo defeat Tilden High School, 46–13.

The 1940 and 42 games each had 75,000 fans, meaning Leo has played in front of four of the 11 largest crowds in Illinois high school history.