Complex sentence: The school has a community service program, which operates in conjunction with St. Mark's, and which requires every upper school student to perform at least 15 hours of service every year, although many students far exceed this quota.
Split into simpler sentences: The school has a community service program, which operates in conjunction with St. Mark's. The program later requires every upper school student to perform at least 15 hours of service every year, although many students far exceed this quota.