Membership is voluntary and renewable annually.
Upon establishing membership, each school adopts and agrees to abide by the IHSA Constitution and By-laws, which have been approved by majority vote of the membership. The Legislative Commission functions as the IHSA's screening committee for proposed amendments to the Constitution and By-laws. Proposals receiving majority support in the Commission are then submitted to all member schools in a referendum. Regular annual voting takes place in the fall. Each member school has one vote.