Complex sentence: Mount St. Mary Academy competes in the Skyland Conference, which is made up of public and parochial high schools spanning Somerset, Hunterdon, and Warren counties in northern New Jersey, operating under the jurisdiction of the New Jersey State Interscholastic Athletic Association (NJSIAA).
Split into simpler sentences: Mount St. Mary Academy competes in the Skyland Conference, which is made up of public and parochial high schools spanning Somerset, Hunterdon, and Warren counties in northern New Jersey. The conference operates under the jurisdiction of the New Jersey State Interscholastic Athletic Association (NJSIAA).