The Morris Hills High School Scarlet Knights compete in the Northwest Jersey Athletic Conference, which is comprised of public and private high schools in Morris, Sussex and Warren countyies, and was established following a reorganization of sports leagues in Northern New Jersey by the New Jersey State Interscholastic Athletic Association (NJSIAA). The school had previously participated in the Iron Hills Conference, which included schools in Essex, Morris and Union counties. With 985 students in grades 10-12, the school was classified by the NJSIAA for the 2019–20 school year as Group III for most athletic competition purposes, which included schools with an enrollment of 761 to 1,058 students in that grade range. The football team competes in the Patriot White division of the North Jersey Super Football Conference, which includes 112 schools competing in 20 divisions, making it the nation's biggest football-only high school sports league. The school was classified by the NJSIAA as Group IV North for football for 2018–2020.