Peekskill students prepare for the New York State Regents Exams in science, language, mathematics, history and English.
The current school is located on the former grounds of the original Peekskill Military Academy, which closed in 1968.
Most were given credit for a "co-op" work experience program that the district had discontinued years earlier.
Superintendent James Willis said in a letter to parents, "The Board of Education and I, along with my administrative team, are absolutely appalled by what we have discovered.
Moving forward, I am organizing an internal protocols team to assess the current transcript review processes and to make recommendations to ensure something like this can never happen again."
The words of the school song were written in 1932 by Edwin Steckel, music teacher and bandmaster.