Complex sentence: The Covenant School has beaten St. Anne's-Belfield School in every sport but didn't play the Covenant School in football when the Covenant School was the best in the state back in the early 2000's.
Split into simpler sentences: The Covenant School has beaten St. Anne's-Belfield School in every sport. STAB didn't play the Covenant School in football when the Covenant School was the best in the state back in the early 2000's.