The last time the Old Rochester Regional High School boys basketball team played in the Division III state semifinals was in the 1988-1989 season, and that team lost to North Cambridge Catholic.

The 2014-15 team is headed to the state finals.

The South Sectional champion Bulldogs once again put forth a complete team effort. Tough defense and rebounding sparked a successful up-tempo offense, leading ORR to a 61-48 win at TD Garden Tuesday afternoon against the North Sectional winner Pentucket Regional High School.

“Defense — defense is always our main focus,” said ORR junior forward Evan Santos. “Even if we’re having a bad shooting day, we’re going to make theirs a worse shooting day. That’s pretty much our motto.”

Up 12-2 after the first quarter, Old Rochester (22-3) never trailed in the contest. The Sachems were able to trim the lead to as few as six several times, including in the fourth quarter, but in the end, the Bulldogs were just too tough.

A 7-0 run about midway through the fourth quarter put Old Rochester up 47-36. The scoring spurt was keyed by a big three-pointer from senior guard Ryan Beatty. It was followed by a layup from junior forward Will Santos off a Jordan Menard (senior guard) steal.

Beatty had seven of his 13 points in the fourth quarter.

“They’re a confident, loose group right now,” Head Coach Steve Carvalho said following the game. “They’re very loyal to each other. We call ourselves ‘Brothers in Arms.’ Their mindset is confident.”

Pentucket’s leading scorer, the 6’3” sophomore forward Patrick Freiermouth, had 18 points, but no other player on the Sachems (17-6) was able to muster up double digits.

Santos and brother Evan, who split defensive duties on Freiermouth, both wore Martin Luther King-inspired socks to the game. Though their dream of winning a state championship is something they share, the twins had different emotions coming into the game.

“It was crazy,” said Will, who led ORR with 16 points, including eight in fourth quarter. “At first I was really, really nervous. But as the game went on, I got used to it. It was awesome.”

Initially, his brother Evan felt the opposite way.

“I think I was maybe a little too calm,” he said. “I think if I was a little more nervous, I would have come out stronger.”

Still, playing in the same building as Boston Celtics legends left a lasting effect on both brothers and the rest of the ORR squad.

“It’s crazy,” said Will. “It’s awesome because you watch it on T.V. and see it from the stands, but it’s nothing like actually being on the floor level.”

Freshman point guard Noah Fernandes (nine points) also played well for ORR, as did Menard, who finished with 13 points.

Old Rochester Regional will face the winner of a matchup between Uxbridge vs. Hoosac Valley, who face off Wednesday evening. The final game will be at the DCU Center in Worcester at 12:30 p.m. Saturday.

“I’ll be going out to Springfield tomorrow to take a look at them,” said Carvalho. “I certainly like our chances. I think we’re the team to beat, but who knows at this point? We’re going to have to play excellent basketball. We’ll be well-prepared.”

“We’ll just keep playing our game,” added Will Santos. “We’ve gotta see what this other team looks like first.”