DANVERS — As Red Sox broadcaster Ned Martin used to say: “Mercy!”

St. John’s Prep and BC High went up and down the field with impunity Friday, with The Prep winning the Division 1 quarterfinal matchup, 56-34, in a game that wasn’t even that close.

Top-seeded St. John’s will play No. 4 Andover next weekend (date and time TBD).

Even though The Prep won, the statistics in this game were a little bit funky too. BC High’s Eagles threw the ball 31 times between their two quarterbacks (Carter Carroll and Kise Flannery), completing 19 for 381 yards. On the other hand, The Prep barely passed. And while St. John’s stayed mainly on the ground, its leading rusher, Cam LaGrassa, only had 102 yards. Jim Nardone chipped in with 54.

St. John’s only had one multiple-touchdown performance, and that was by backup runner Jeff Quigley.

“We didn’t play well at all in the first half,” said Prep coach Brian St. Pierre, discussing his team’s 22-18 halftime deficit. “We were shaky for some reason. I don’t know what it was.”

St. Pierre said the Eagles had only been behind for five minutes during the season until falling behind Friday night.

“But,” he said, “the benchmark of our program is our character and we sure showed that tonight.”

BC High, which lost to The Prep last month, showed that it had come to play, taking the opening kickoff and returning it to the Prep 34. Four plays later, Marshall Rice caught a halfback option pass from 27 yards out for the opening score, putting BC High out front, 8-0.

It looked as if BC High would go up by two touchdowns moments later, but Grayson Ambrosh scooped up a fumble inside the Prep 5 and ran it back for the score, getting the conversion to make it 8-8.

“Big play,” said St. Pierre. “Any defensive score is a big play, but he made a nice play on that.”

Undaunted, BC High came right back, capping a four-play drive with a 62-yard strike down the far sideline from Carroll to Rice to make it 14-8. But back came The Prep, with Jack Angelopolus hauling in a 50-yarder from Deacon Robillard, with Langdon Laws’ PAT making the score 15-14.

The second quarter opened with a long Prep drive that, even though it began on the BC High 43, took almost nine minutes, with Laws’ 22-yard field goal making it 18-14.

However, before the half ended, Carroll, from his own six, found Jacob Bierenbroodspot over the middle, and the speedy receiver did the rest of the work to put BC High up, 22-18 at the half.

It was a different Prep team that took the field after the break. LaGrassa, on the first play, scored on a 50-yard run to put St. John’s back up top, 25-22.

“That was huge,” said St. Pierre. “We talked about how we needed better effort, and they came out and scored right away.”

Another Laws field goal made it 28-22, and the Eagles poured it on from there. Gael Garcia pounded one in from the three, Robillard ran one on from the 35, and Quigley from the nine to make the score 50-22.

From there, the JVs finished out the game, with BC High sandwiching two late touchdowns around Quigley’s 9-yard run.