Complex sentence: Clarke became a music teacher at Glendora High School and was a music director at Mark Keppel High School, Alhambra, California, from 1965 to 1967.
Split into simpler sentences: Clarke became a music teacher at Glendora High School. Don Clarke was a music director at Mark Keppel High School, Alhambra, California, from 1965 to 1967.