DORCHESTER – Big plays. Make them and you’re probably going to win. Watch someone else make them, you’re most likely going to lose.St. John’s Prep found that out for sure last night at BC High. The Prep wasn’t blown out of the place, like some people might have thought. Instead, the visiting Eagles were picked apart by BC High’s big plays ? and shut down by similarly clutch plays by the BC High defense. The final score, 21-7, was pretty indicative of how the game went.”Big plays,” said Prep coach Jim O’Leary. “You can’t give them up, and you have to make them.”We’re going to see the films of this game, and we’re going to see five or six plays that could have made a difference. Third-down passes by them, turnovers by us ?”I can’t fault our effort,” he said. “The kids played hard. That’s a good football team, and they have some great players. But we just couldn’t come up with big plays ? big stops.”The Prep defense bottled up BC High captain Kyle Ewanowski, who only managed 60 yards and a touchdown. But The Prep, 5-5 heading into its Thanksgiving Day game, gave up two long, costly screen passes – one of them for a touchdown – and that clearly frustrated O’Leary.The first of the long gainers came from 27 yards out in a fog so thick you probably could have sliced it with a knife. Sitting on the Prep 27 with a third-and-11, BC High quarterback Bill Kiley found two Prep defensive linemen in his face, one of whom actually got a hand on the screen pass intended for Tyler Horan. However, Horan came back, got the ball, disappeared down the far sideline in the fog, and reemerged to run the ball in for the score that made it 7-0.The Prep looked as if it would match that score, taking the ball into the second quarter and all the way down to the BC High 29 with a first down. However, George Sessoms turned his ankle at the end of an eight-yard run that got The Prep its first down, and the drive stalled.”I think if we could have come back and scored there, it would have been a much different game,” said O’Leary.BC High came back with another drive, the key play being another screen pass, this one on a third-and-six from its own 25 when Kiley lobbed one to Niall Murphy, who took it 46 yards down the near sideline, all the way to the Prep 19. BC High needed only three more plays after that before Kiley found Brandon Cipolla for a 22-yard strike to make it 14-0 with 3:19 to go in the half.A crucial turnover on the snap from The Prep’s own 13 gave BC High its final touchdown – this one a six-yard run by Ewanowski with 4:08 left in the third quarter to make the score 21-0.The Prep had another drive stopped on a pass interception at the BC High 28, but the defense forced a three-and-out, giving St. John’s the ball back on the BC High 48. After a 28-yard Greg Donahue-to-Tyler Coppola hookup, Donahue called his own number for a 20-yard touchdown run up the middle to account for the final score.