ALIQUIPPA, Pennsylvania — One month after the Aliquippa High School football team finished the season with a perfect record and a state championship, the Pennsylvania Interscholastic Athletic Association ruled it would have to play up a class for the next two seasons.

Based on its enrollment of 156 boys, Aliquippa High should have been in Class 2A, but the PIAA used a “competitive balance formula” to move it to 5A. The new classification means Aliquippa, with a student body that is largely black and low-income, will compete against suburban, mostly upper-middle class school districts that have enrollments of between 424 and 619 boys.