The Greater Middlesex Conference is an athletic conference comprising 34 public and private high schools located in the greater Middlesex County, New Jersey area. The league operates under the supervision of the New Jersey State Interscholastic Athletic Association. There are both competitions in Middle and High school levels.
| School | Location | School District | Team Name |
| Bishop George Ahr High School | Edison | Roman Catholic Diocese of Metuchen | Trojans |
| Highland Park High School | Highland Park | Highland Park Public Schools | Owls |
| Metuchen High School | Metuchen | Metuchen School District | Bulldogs |
| Middlesex High School | Middlesex | Middlesex Board of Education | Blue Jays |
| Mother Seton Regional High School | Clark | Roman Catholic Archdiocese of Newark | Setters |
| South River High School | South River | South River Public Schools | Rams |
| Spotswood High School | Spotswood | Spotswood Public Schools | Chargers |
East Brunswick High School serves Grades 10–12. Freshmen are housed at Churchill Junior High School, along with the 8th graders.
The following is a list of the sports that the Greater Middlesex Conference offers. Some sports do not have a team from every school, while other sports have teams from all 33 member schools. Each bullet is an individual team (as in one team for girls and one team for boys — not a combined unisex team). For example, although the boys and girls track teams from a single school usually practice together and have meets at the same time, there are separate events at their meets for boys and for girls, and therefore, the teams are scored and compete separately.
Fall sports
| Winter sports
| Spring sports
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Highland Park High School (HPHS) is a four-year comprehensive public high school that serves students in ninth through twelfth grades from the borough of Highland Park, in Middlesex County, in the U.S. state of New Jersey, as the lone secondary school of the Highland Park Public Schools system. The school has been accredited by the Middle States Association of Colleges and Schools Commission on Elementary and Secondary Schools since 1940.
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Cardinal McCarrick High School (CMHS), later known as Cardinal McCarrick/St. Mary's High School, was a Catholic secondary school located in South Amboy, New Jersey, that operated under the supervision of the Roman Catholic Diocese of Metuchen. The school closed at the end of the 2014–15 school year, in the wake of an increasing financial deficit.
Franklin High School (FHS) is a comprehensive four-year public high school serving students in ninth through twelfth grades, located in the Somerset section of Franklin Township in Somerset County, in the U.S. state of New Jersey, operating as the lone secondary school of the Franklin Township Public Schools.
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Middlesex High School (MHS) is a four-year comprehensive public high school located in the center of Middlesex, Middlesex County, in the U.S. state of New Jersey, serving students in ninth through twelfth grades as the lone secondary school of the Middlesex Board of Education. The school is surrounded by Mountain View Park and all of its athletic complexes, including Memorial Field.
St. Thomas Aquinas High School, formerly known as Bishop George Ahr High School, is a private four-year college preparatory and coeducational Roman Catholic high school for students from ninth through twelfth grades. It is located on a campus covering 34 acres (14 ha) in the northern section of Edison, in Middlesex County, in the U.S. state of New Jersey. The school operates under the auspices of the Roman Catholic Diocese of Metuchen.
Monroe Township High School is a comprehensive four-year public high school located in Monroe Township, in Middlesex County, in the U.S. state of New Jersey, serving students in ninth through twelfth grades part of the Monroe Township School District. The school serves students from Monroe Township and approximately 300 from Jamesburg who attend Monroe Township High School as part of a sending/receiving relationship with the Jamesburg Public Schools that has been in place since 1980. The school's mascot is a falcon and the school colors are purple and Vegas gold. The motto is "Excellence is Our Expectation".
Paul VI High School is a private Catholic high school located in Haddon Township, in Camden County, in the U.S. state of New Jersey. As there is no post office in Haddon Township, the mailing address is Haddonfield. The school, founded in 1966, is named in honor of Pope Paul VI and is overseen by the Roman Catholic Diocese of Camden. The school has been accredited by the Middle States Association of Colleges and Schools Commission on Elementary and Secondary Schools since 1979 and is accredited until July 2030.
Spotswood High School is a four-year comprehensive public high school, serving students in ninth through twelfth grade in Spotswood, in Middlesex County, in the U.S. state of New Jersey, operating as the lone secondary school of the Spotswood Public Schools.
Saddle Brook High School is a six-year comprehensive community public high school that serves students in seventh through twelfth grades from Saddle Brook, in Bergen County, in the U.S. state of New Jersey, operating as the lone secondary school of the Saddle Brook Public Schools.
Metuchen High School is a four-year comprehensive public high school that serves students in ninth through twelfth grades from Metuchen in Middlesex County, in the U.S. state of New Jersey, operating as the lone secondary school of the Metuchen School District. The school has been accredited by the Middle States Association of Colleges and Schools Commission on Elementary and Secondary Schools since 1929.
Old Bridge High School is a four-year comprehensive public high school that serves students in ninth through twelfth grades from Old Bridge Township in Middlesex County, in the U.S. state of New Jersey, operating as the lone secondary school of the Old Bridge Township Public Schools. The school is located on County Route 516 in Old Bridge Township, however, it is assigned a Matawan mailing address. The school has been accredited by the Middle States Association of Colleges and Schools Commission on Elementary and Secondary Schools since 1970.
Warren Hills Regional High School is a four-year public high school located on Jackson Valley Road in Washington Township in Warren County, in the U.S. state of New Jersey, operating as part of the Warren Hills Regional School District. The school offers a comprehensive education for students in ninth through twelfth grades. The student population includes students from Franklin Township, Mansfield Township, Oxford Township, Washington Borough and Washington Township. The school has been accredited by the Middle States Association of Colleges and Schools Commission on Elementary and Secondary Schools since 2014.
East Brunswick Magnet School is a four-year career academy and college preparatory magnet public high school serving students in ninth through twelfth grades located in East Brunswick in Middlesex County, New Jersey, United States, operating as part of the Middlesex County Magnet Schools. The school serves students of many diverse cultures from all over Middlesex County.
Perth Amboy Technical High School is a four-year career academy and college preparatory magnet public high school for students in ninth through twelfth grades located in Perth Amboy in Middlesex County, New Jersey, United States, operating as part of the Middlesex County Magnet Schools. The school serves students from all of Middlesex County.