Simplify the following text for a Grade 7 native English-speaking person.
Original: In his autobiography , Davis criticized the Juilliard classes for centering too much on the classical European and `` white '' repertoire . However , he also acknowledged that Juilliard helped give him a grounding in music theory that would prove valuable in later years .
Simplified: He also said that his Juilliard classes helped him to understand music theory .