Complex sentence: MHS & Whitehaven split 2011 & 2012 Titles respectively, and each had earned undefeated regular Season records prior to their 2011 6A Title contest, and 2012 rematch.
Split into simpler sentences: MHS & Whitehaven split 2011 & 2012 Titles, respectively. Both MHS & Whitehaven had earned undefeated regular Season records prior to their 2011 6A Title contest, and 2012 rematch.