Westlake High's defense produced four turnovers and limited defending champion Arroyo Grande to 190 total yards in a 24-7 victory Saturday night in a Southern Section Division IV semifinal at Arroyo Grande.
Westlake (12-1) will play for its first championship since the school opened in 1978. The Warriors will meet San Luis Obispo on Friday night at Cal Poly San Luis Obispo.
Take away a 72-yard touchdown run in the second quarter by Chris Janowicz, and Arroyo Grande (10-2) would have been shut out on its own field.
Westlake linebacker Ben Lorier made three tackles for losses and recovered a fumble.
Westlake's offense came through with two decisive drives in the third quarter to turn the game into a rout.
With Westlake holding a 10-7 halftime lead, quarterback Zac Wasserman led the Warriors on a 55-yard drive, twice picking up first downs on third-down passes. Julian Lambert reached the end zone with a 16-yard touchdown run for a 17-7 lead.