Mt. Blue High School’s Caleb Haines (13) rushes for yards against Lawrence High School in the first quarter in Fairfield on Friday. (Michael G. Seamans/Morning Sentinel)

FAIRFIELD — With Mt. Blue’s defense shutting down its team’s offense in the first half, the Lawrence coaching staff went old school.

“They were doing a lot of adjusting to our regular formations, so Coach Lindlof (offensive coordinator Ken Lindlof) said let’s just get into our double tights with a T backfield and see if we could just get into a rhythm,” Lawrence head coach John Hersom said.

The full house backfield is hardly innovative, but for the Bulldogs on Friday night at Keyes Field, it was effective. Lawrence scored three touchdowns in the second half, and pulled out a 20-13 win over Mt. Blue in the Class B South football quarterfinals.

No. 4 Lawrence, now 5-4, will face No. 1 Skowhegan (5-3) next week. No. 5 Mt. Blue ends the season at 4-5. For a Lawrence team that began the season 0-2, advancing to the regional semis was a welcome step.

“We all thought we could do it. At the beginning of the season it wasn’t happening. Now it is,” said senior running back Isaiah Schooler, who scored a pair of touchdowns and ran for a game-high 120 yards.

Down 6-0 at the half, the Lawrence formation switch paid off immediately. Schooler took the first play of the second half and ran 46 yards to the Cougars’ 4 before being pushed out of bounds. Schooler scored on the next play, and Christian Adams’ extra point gave the Bulldogs the lead for good, 7-6.

With 3:50 to play in the third quarter, Kyle Carpenter’s 6-yard touchdown run increased Lawrence’s lead to 14-6. Schooler scored again with 11:39 left in the game, on another 4-yard run, and Lawrence led 20-6.

“We could see that they (Mt. Blue) were kind of unsettled,” Hersom said. “It was just straight ahead running plays. We thought we could stay with that and move the ball. We’re willing to take those small chunks and keep the chains moving.”

Lawrence gained 274 yards, with 213 coming in the second half. Carpenter added 100 yards on the ground.

Mt. Blue won the regular-season game against Lawrence, 34-13 in Week 1 of the season, by dominating on the ground. In the first half, it looked as if the Cougars might do that again. Mt. Blue put together a 13-play, 72-yard drive, taking a 6-0 lead on Kevon Johnson’s 1-yard touchdown run with 6:34 left in the second quarter.

That was the only long drive the Cougars could muster until the fourth, when they scored with a well-executed trick play. Facing fourth-down-and-6 from the Lawrence 10, wideout Noah Bell took the ball on a reverse, pulled up, and fired a touchdown pass to quarterback Hunter Meeks in the back of the end zone. The touchdown cut Lawrence’s lead to 20-13 with 4:11 to play, but out of timeouts, Mt. Blue never got the ball back. Alex Higgins recovered the onside kick, and the Bulldogs ran out the clock.

Johnson led the Cougars with 77 yards on 15 carries.

Mt. Blue High School’s Noah Bell (4) leans back for an underthrown ball as Lawrence High School’s Kyle Carpenter (20) defends Fairfield on Friday. (Michael G. Seamans/Morning Sentinel)

Lawrence High School’s Alex Higgins (45) makes a reception as Mt. Blue High School’s Zack Delano (34) tries to defend in the first quarter Fairfield on Friday. (Michael G. Seamans/Morning Sentinel)

Mt. Blue High School’s Randy Barker (12) tackles Lawrence High School’s Nate Bickford (7) in the first quarte Fairfield on Friday. (Michael G. Seamans/Morning Sentinel)