Franklin rallied with 23 unanswered points in the fourth quarter to shock the Lightning and earn a trip to the state title game.
The Sabers (12-1) will play Sun Prairie (13-0) in the championship game next Friday at Camp Randall Stadium.
North (10-3) led 19-3 after the third quarter on the strength of a pair of touchdown passes from Matthew Schecklman of 62 and 3 yards to Damian Borland and Alex Heran, respectively.
Schecklman also had a 3-yard touchdown run, but Franklin quarterback Myles Burkett got the Sabers offense on track in the fourth quarter. He completed touchdown passes of 11 and 45 yards and also had a pair of 2-point conversion passes.