In December 1930, five private religious and secular schools in the Chicago area came together to create an athletic conference for non-public schools. The five schools weren Chicago Christian of Palos Heights, Chicago Luther Institute, Wheaton Academy, Chicago Central YMCA, and the Pullman Free School of Manual Training in Chicago. Initially the conference was organized for basketball only; however, as time progressed, the conference added other sports.
Luther Institute split into Luther North and Luther South in 1953, and in 1954, Elgin Academy, Glenwood School, and North Shore Country Day School joined the conference. In 1955, Walther Lutheran High School (Melrose Park) joined the league. With these additions, the league divided into two divisions with a championship game between the division winners. The championship game was dropped after 1957 but the division set up remained until 1966 when 6 schools left to form the Independent School League. Those schools were Chicago Latin, Elgin Academy, Francis W. Parker School, Glenwood School for boys, Morgan Park Academy, and North Shore Country Day. Morgan Park Academy had joined in 1960, however, it was included with the six teams that exited the conference and with Chicago Harvard leaving the conference in 1962, it left the league with a total of seven teams at the beginning of the 1967 school year.
North Park Academy departed the conference in 1969, Wheaton Academy left in 1971. To replace them, Little Flower Academy and Providence Catholic High School were added in 1971. Aurora Central Catholic High School was added in 1973 when Little Flower Academy closed, keeping the league at seven members as the 1970s came to a close.
The Private School League had 29 teams throughout its history, the list of schools encompasses all of the schools which were once a part of the conference.