Williams, a Texas A&M recruit, finished with 197 yards and scored on runs of 2, 5 and 24 yards for the Wildcats (14-2), who ended Cibolo Steele's 28-game winning streak and dethroned last year's champions.
Tommy Armstrong had two touchdown passes for the Knights (15-1), who scored first. Dekaney struggled early, largely because of false-start penalties -- four in five plays at one point -- and was stopped another time on four plays at the Steele goal line. But D'Juan Hines threw a 40-yard touchdown pass to Austin Garrett to get the Wildcats on the board.
Up to that point, penalties had accounted for Dekaney's biggest gains, on two personal foul calls against Steele. But the Wildcats led 20-7 at halftime and the Knights didn't score again until the final four minutes of the game.
Jarrett Irving, who had two interceptions in spearheading a defense that held Steele to 164 yards from scrimmage, was the game's defensive MVP.