MIDDLETON – The three-bulletin checklist of goals the modern-day St. John’s Prep boys hockey team sets each preseason now has just one box left to check off.

Behind a 4-for-6 success rate on the power play and a dominant defensive performance to allow just nine shots on net, the No. 1 Eagles (12-1) clinched their first Catholic Conference title since 2013 Saturday afternoon with a convincing 6-1 win over No. 2 Xaverian (9-4) for their 12th straight victory.

Senior Brady Plaza orchestrated much of the offense with three assists on the man-advantage, with senior Christian Rosa potting two of them on vicious one-timers that sent a rowdy student-section into an uproar. Four of the goals came in the third period to separate from a one-goal lead at the second intermission, capping off a showcase of blocked shots and physical defensive plays that limited the Hawks.

After also taking the Pete Frates Winter Classic for the first time since 2015 in December, two of St. John’s Prep’s major goals are accomplished.

Winning the Div. 1 state championship is next.

“Obviously it’s really difficult to win a Catholic Conference championship,” said Eagles head coach Kristian Hanson. “We’ve won two state titles (since 2013) but no conference titles. … We do have to recognize and enjoy these moments.”

“It’s awesome, it’s a great feeling,” Rosa added. “But it’s just one of our three goals. … It’s awesome, we’ll live it up today, but then we’ve got to put it behind us.”

Xaverian put St. John’s Prep behind early, taking advantage of early limited opportunities with a goal from Sean Pohl in the first three minutes. But once the Hawks’ penalties started coming, that 1-0 lead didn’t last long.

Just 13 seconds into the Eagles’ first power play, Plaza sent a pass to the top of the left circle from the point for Rosa to uncork a one-timer past Cole Pouliot-Porter for the 1-1 tie. With four minutes left in the first, SJP then needed only 22 seconds for Plaza to send the same pass to the right. Cam Umlah snapped in the 2-1 advantage.

“When you’re up top … they like to lean in and go for the block,” Plaza said. “We just knew that if we got the opportunity, we have two really good shooters, Rosa and Umlah. With those opportunities we were able to score.”

The second period saw the ice tilted in St. John’s Prep’s favor. Pouliot-Porter stood on his head with 15 saves in the frame to keep SJP from extending its lead, and the Hawks drew a power play in the final minute to head into the third with 1:15 of an advantage left.

But a successful penalty kill from the Eagles maintained the lead, and another Xaverian penalty in the first couple minutes of the third led to another SJP power play. Plaza found Rosa again to make it 3-1, and the floodgates opened from there. Ethan Goodrich scored his first goal five minutes later, Hunter Steiner did the same to make it 5-1, and JR Goldstein put the final bow on the win.

Scoring six goals against Xaverian is bound to draw a lot of praise. But the defensive performance, with multiple guys limping off from blocked shots, was just as noteworthy.

“It all starts with that blocked shot, then the bench goes crazy,” Rosa said. “Everyone wants to block a shot, everyone’s just for the team today.”

Xavarian’s Ben Kramer is upended by Caleb White of St. John’s Prep during a boys hockey clash Saturday. (Staff Photo/Stuart Cahill/Boston Herald)