NEPSAC oversees the policies, procedures and administration of administration of interscholastic competition between member and associate schools, including some of the oldest and fiercest high school rivalries in the United States. Member schools field a wide variety of athletics programmes including: Basketball (Boys & Girls); Cross Country (Boys & Girls); Diving (Boys & Girls); Field Hockey (Girls); Football (Gridiron) (Boys); Golf (Boys & Girls); Ice Hockey (Boys & Girls); Lacrosse (Boys & Girls); Soccer (Association Football) (Boys & Girls); Skiing (Boys & Girls); Squash (Boys & Girls); Swimming (Boys & Girls); Tennis (Boys & Girls); Volleyball (Girls); Water Polo (Boys & Girls); and Wrestling (Boys & Girls). In addition, many of the schools maintain successful baseball programmes competing against one another under the auspices of NEPSAC. Outside of NEPSAC, many of the member schools also participate in New England Interscholastic Rowing Association competitions.

Members are drawn from leading prep schools in the Northeast region (with most being accredited by the New England Association of Schools and Colleges) and are allocated to one of four regions, however member schools are not restricted from participating in leagues unaffiliated with NEPSAC. That being said, most NEPSAC member schools have long-competed in interscholastic sports against one another or as part of NEPSAC affiliated leagues including: the Eastern Independent League; the Fairchester Athletic Association; The Founders League; the Girls Independent League; the Housatonic Valley Athletic League; the Independent Girls Conference; the Independent School League; the Lakes Region League; the Maine Association of Independent School Athletic Directors League; the Massachusetts Bay Independent League; and the Southeastern New England Independent Schools Athletic Association. A number of schools from outside the New England region are also members or associates of NEPSAC – competing in programmes where local competition may not be available or of the same standard or where they are located geographically closer to NEPSAC member schools than to other schools in their domestic league structures (this is typically the case for those Canadian member schools).

Whilst membership of NEPSAC has remained fairly consistent since its foundation, please check www.nepsac.org for details of current membership status.