For an uncertain amount of time, Aaron attended a military academy up until he transferred to Phoenix Drop High School at the start of his senior year. Derek forced him to go to this military academy under the guise of believing it would teach Aaron emotional control, and therefore the discipline required to control his Ultima powers.
Phoenix Drop High (Season 1)
Aaron transforms from a class delinquent and outcast to a quiet confidant and someone who user can depend on. Initially, he is hostile