The Class AA boys’ basketball tournament is scheduled to begin next week, but Portland and South Portland produced a regular-season finale full of postseason excitement Thursday night at the Portland Expo.

In a fourth quarter that featured four lead changes, it was a familiar hero – Red Riots senior Jaelen Jackson – who hit the decisive shot, a putback with three seconds left as the Red Riots eked out a 47-46 victory.

“I keep getting lucky being in the positions I am,” said Jackson, who finished with 11 points as South Portland finished the regular season at 15-3. “Obviously, we’d love to win by more, but a win’s a win.”

Pitia Donato broke a 43-43 tie with a free throw with 2:21 to go, but Ben Smith got a jumper to put the Red Riots back on top.

Then, with 48 seconds left, Donato set up Jeissey Khamis for a layup and it looked like the Bulldogs might pull it out, but after Gabe Galarraga missed his second straight free throw with five seconds on the clock, Jackson got the rebound and floated it home to end it.

“As soon as (Gabe) shot it, I just stayed low and got the ball,” said Jackson. “I was just so focused that I didn’t even hear the crowd.”

“Jaelen’s not afraid to miss and I think that’s huge,” added South Portland Coach Kevin Millington. “He was going to get his hands on the ball somehow.”

After a sluggish start, the game was tied 2-2 midway through the first quarter, Manny Hidalgo came off the bench for South Portland and scored four points to spark a run, which also included a long 3-pointer from Jackson and a slam dunk from Galarraga, to produce a 13-6 advantage.

Galarraga then scored eight points in the second period and the Red Riots went ahead by 10, but with time winding down, Remijo Wani capped his 12-point half with a layup, then Kennedy Charles drove the floor and finished at the rim to pull Portland within 28-22 at the break.

The Bulldogs nearly came all the way back in the third quarter, cutting the deficit to one, 30-29, but Galarraga was unstoppable on the glass, three times scoring on putbacks. Wani then gave Portland a little life with a layup at the horn, cutting the Red Riots’ lead to 38-35.

Galarraga led South Portland with 18 points and seven rebounds, including six on the offensive glass.

Portland (13-5) got a game-high 22 points from Wani and 13 from Khamis.

The Bulldogs expect to be the No. 2 seed in Class AA North.

“It was another exciting high school game,” said Bulldogs Coach Joe Russo. “It would have been more fun to pull it out. We had our opportunity on a missed free throw and didn’t secure the ball and that’s why we lost.

“We did a lot of nice things tonight that I was really pleased with, but you can’t give a good team extra opportunities.”