GREAT BARRINGTON — At halftime, visiting Mahar Regional School had sliced away most of Monument Mountain Regional High School’s double-figure lead. It was something the Senators had done to other teams.

And when Mahar’s Sophia Apteker hit a foul-line jumper to open the third quarter, it was a two-possession game. Destiny Brown and the Spartans had other ideas.

Brown scored three straight points, starting a 14-3 run, and the seventh-seeded Spartans held the 10th-seeded Senators at arm’s length the rest of the way, pulling ahead for a 64-44 win in Monday’s Western Massachusetts Division III Girls’ Basketball Tournament first-round game.

“We needed to make a run at them in the third quarter and really couldn’t,” Mahar coach Larry Fisher said. “I’m proud of the way my kids kept coming back and didn’t give up.”

Meri Powell and Brown scored 18 points each for the Spartans, while Fiona Horan had a double-double with 16 points and a game-high 16 rebounds. Powell and Brown each scored 5 points in the third quarter for the Spartans (12-9), who advance to the D-III quarterfinal round against idle, second-seeded South Hadley High School. That game will be played at South Hadley Thursday at 7 p.m.

Jasmine Vautour scored 2 points in the first half and finished with 11 points and a team-best 11 rebounds. Hannah Paul scored 11 points for the Senators, had 6 rebounds and 4 steals.

The Spartans forced 28 turnovers, 15 in the second half. Powell and Brown each had 5 steals.

“We pressed them and after a while they got tired of looking at us. They got tired of the press,” said Fisher. “That’s where we cut it down before the half.

“We cut it to six in the third quarter and we couldn’t come back.”

The Spartans held a 26-18 halftime lead after being held without a point over the last 3:40 of the second quarter. The Senators scored first when Apteker caught a pass from Vautour at the foul line and swished the shot.

On Monument’s next possession, the Spartans moved quickly into the front court and Brown caught a pass from Alexa Troiano for a hoop. Then Horan snared a defensive rebound, Brown was fouled, and she made 1 of 2 from the line. That made it 29-20, and the Spartans had regained the momentum.

The Spartans extended their lead to 17 points on five unanswered points by Powell, who had 5 steals to go with her 18 points. The Senators got the lead down to nine points, trailed by 10 after three and never caught up.