Complex sentence: After graduating from high school two years early at age 15, Mitchell joined local Vancouver pop-rockers William Tell & the Marksmen, and later became a member of the "psychedelic sixties" era band, the Seeds of Time.
Split into simpler sentences: After graduating from high school two years early at age 15, Mitchell joined local Vancouver pop-rockers William Tell & the Marksmen. He later became a member of the "psychedelic sixties" era band, the Seeds of Time.