The University High School Phoenix compete in the Super Essex Conference, which is comprised of public and private high schools in Essex County and was established following a reorganization of sports leagues in Northern New Jersey by the New Jersey State Interscholastic Athletic Association (NJSIAA). Prior to the NJSIAA's realignment in 2010, the school had competed in the Colonial Division of the Colonial Hills Conference, which included public and private high schools in Essex, Morris and Somerset counties. With 381 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Group I for most athletic competition purposes, which included schools with an enrollment of 75 to 476 students in that grade range.