Complex sentence: Mansfield Summit's varsity football held an 11-0 record in city play, never losing to another Mansfield School, until October 3,2008 when Summit lost to Mansfield High School in a 21-14 upsetting end to their arsenal of victories.
Split into simpler sentences: Mansfield Summit's varsity football holds an 11-0 record in city play, never losing to another Mansfield School. Until October 3,2008 when Summit lost to Mansfield High School in a 21-14 upsetting end to their arsenal of victories.