The ball slipped as it rolled off Khalen Cumberlander’s hand. With the score tied and precious few seconds on the clock, Coolidge’s standout senior guard was worried that his potential go-ahead free throw, the front end of a one-and-one, would barely get to the rim.

It had not been the best of nights for Cumberlander, the Colts’ leading scorer. But it ended in a jubilant celebration that continued well into the locker room.

Cumberlander’s free throw had just enough oomph. It kissed off the front of the rim, caromed off the backboard and fell through the basket, lifting Coolidge to the biggest upset so far in the Washington area high school basketball season. Cumberlander’s second free throw, with decidedly less pressure, gave the host Colts a 51-49 victory over second-ranked Montrose Christian in a nonleague game Thursday night in Northwest Washington.

“I thought it was going to be short,” said Cumberlander, a Central Connecticut State recruit. He said he was praying and talking to himself during a timeout that preceded the free throws.

It was a thrilling finish to a game that was close throughout. Junior forward De’Shaun Morman matched his season high with 28 points for Coolidge (18-4), which won its ninth consecutive game. Virginia recruit Justin Anderson was just as good for Montrose Christian. He scored 14 of his 23 points in the third quarter as the Mustangs (13-2) seemed to take control.

Neither team led by more than three in the fourth quarter. Morman’s three-pointer from the top of the key, with a hand in his face, gave Coolidge a 49-47 lead with 59 seconds left. Anderson countered with two free throws with 43 seconds left to tie the game.

Coolidge worked the clock for a final shot. Montrose, which had won its previous eight games, had a foul to give and used it with five seconds left, but on the following inbounds play, Cumberlander caught a pass and was fouled.

“Khalen kind of forced the action” on the decisive play, Colts Coach Vaughn Jones said. “He’s been our go-to guy the last two years. It was fitting he had a chance to win the game for us.

“Montrose beat us bad last year, kids don’t forget that. These kids are very tough. . . . You beat Montrose Christian, that’s definitely a feather in our cap. But our goal is to win the DCIAA.”