PLANO – Strange things can happen in rivalry games, but Plano's relentless offense kept Plano East from entertaining thoughts of an upset Thursday night at Clark Field.

A 21-point third quarter allowed Plano to pull away for a 51-20 win Thursday at Clark Field.

Plano, 5-0 and ranked No. 2 in the state, scored on its first three possessions in the second half after holding just a 10-point lead, 30-20, at halftime.

Running back Rex Burkhead carried 13 times for 128 yards and caught three passes for another 46 yards to lead Plano. He scored three touchdowns and returned a fumbled two-point conversion try 98 yards for two more points.

Plano East (0-5) has now lost nine games in a row dating to last season, but it showed the fire one would expect in a rivalry game. After spotting Plano a 14-0 lead in the first quarter, Plano East scored on its next two drives to nearly pull even.

Toben Opurum, who carried 17 times for 99 yards, tossed a 21-yard touchdown to quarterback Ryan Foster on a double pass for Plano East's first score.

After a 3-yard touchdown by Opurum made it 14-13 Plano, pending the extra point, Plano East faked the kick and instead tried to run the ball in for two points. Burkhead picked a loose ball out of the pile and sprinted the other way for a 16-13 Plano lead.

Plano quarterback Carson Meger then tossed a pair of 40-yard touchdown passes, one to Holt Hoetger and the other to Kris Lott, on back-to-back possessions.

Plano East rallied to score just before halftime and cut the lead to 10. But after Plano scored on the opening drive of the second half, Plano East could not convert a fourth-and-one at midfield.

Meger threw his fourth touchdown pass of the night. Then Burkhead carried in from 10 yards out for a 31-point advantage with 3:20 left in the third quarter.