Simplify the following text for a Grade 14 native English-speaking person.
Original: By the age of sixteen , Hahn had completed the Curtis Institute 's university requirements , but elected to remain at the Institute for several more years to pursue additional elective courses , until her graduation in May of 1999 with a Bachelor Of Music degree .
Simplified: By sixteen , Hahn had completed the Curtis Institute 's university requirements , but elected to remain for several years to pursue elective courses , until her graduation in May 1999 with a Bachelor of Music degree .