It is a member of the National Federation of State High School Associations.

The classification thresholds are periodically adjusted so as to result in an approximately equal number of teams in each class.

Schools may petition the NHIAA to play in a class higher than that in which they would otherwise be placed.

For some sports (e.g. football or ice hockey), competition is not organized based on school class, but based on divisions established by the NHIAA committee governing the individual sport.

Classifications for the 2022–23 and 2023–24 seasons are as follows:[1] The NHIAA sanctions competitions in the following sports: