The Phillipsburg High School Stateliners compete as a member of the Skyland Conference, which is comprised of public and private high schools in Hunterdon, Somerset County and Warren counties, and operates under the supervision of the New Jersey State Interscholastic Athletic Association (NJSIAA). With 1,242 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Group IV for most athletic competition purposes, which included schools with an enrollment of 1,060 to 5,049 students in that grade range. The school was classified by the NJSIAA as Group IV North for football for 2018–2020. The school had been a member of the Pennsylvania Interscholastic Athletic Association's defunct East Penn Conference.