Complex sentence: Dillon enrolled in and completed the Meisner training program at The Actor's Workshop of Ithaca, beginning during their junior year of high school at age sixteen, the youngest student ever admitted to the class.
Split into simpler sentences: Dillon enrolled in and completed the Meisner training program at The Actor's Workshop of Ithaca, beginning during their junior year of high school at age sixteen. They were the youngest student ever admitted to the class.