BIDDEFORD — When Thornton Academy players cross the Saco River to play rival Biddeford High in the Biddeford Ice Arena, the atmosphere is loud and spirited. Cheers, boos and maybe a taunt or two between the student sections.

One of the best rivalries in boys’ hockey.

For girls’ hockey, this season Biddeford players and Thornton players gather in the Biddeford Ice Arena – skating together – on the same team.

“This is a big rivalry and it was kind of weird at first,” said Biddeford High senior goalie Rebekah Guay.

“But we’ve got a lot of numbers this year. It’s awesome to know we have that many girls on the ice.”

Biddeford High, which has had its own team since girls’ hockey became a sanctioned sport in 2008-09, had 23 players going into the season. Thornton, which has never fielded a girls’ hockey team, is providing five more players for the new Biddeford/Thornton team.

The idea for the co-op team was Biddeford’s.

“I thought it was a no-brainer for us if we want to maintain these numbers,” said Coach Ashley Potvin. “If we want to get more girls in the area skating, it made sense.”

Of the 16 teams suiting up this season, only four have rosters with players exclusively from their schools – Falmouth, Greely, St. Dominic and Brunswick.

Biddeford has always attracted players – and 23 is larger than most rosters – but Potvin said more is better. Inexperienced players can be eased into varsity play.

“Because of the co-ops, it allows every team to have not just 6-7 junior varsity skaters but 12 to 15,” she said. “Not only does it do wonders for our teams, it does wonders for the sport, getting girls out to play.

“It seems we have gone back to the roots of how girls’ hockey started in Maine. When I was a club player in Biddeford, we had girls from (Thornton), from Massabesic … it was more of a regionalized thing.”

Biddeford, always a popular hockey town, took pride in having its own team. But enrollment has declined (from 934 to 775 the past 10 years), and the sport has not grown.

“The numbers are going down, even on the boys’ side, and they don’t look like they’re getting much better in the very near future,” said Biddeford High Athletic Director Dennis Walton.

“This seemed to make sense. We have experience with co-op with Thornton Academy, but with individual sports – swimming, indoor track, etc. This is our first go-around with an actual combined team. But it’s good for the kids.”

The Biddeford/Thornton jersey features “Tigers” across the front with a maroon and gold Trojans patch on one shoulder.

Biddeford finished 6-12 last year and reached the playoffs, losing in the first round. The Tigers lost this season’s opener Friday, 4-0 to Scarborough.

“Hopefully we’ll go a little further with the help of the (Thornton) girls,” said Guay, a Maine Sunday Telegram All-State choice last year.

Ashley Atwater planned to play another season on the Thornton junior varsity boys’ team, until the co-op team surfaced.

But, playing with Biddeford?

“Uh, this might be a problem,” Atwater thought at first. “But from the first practice, we all got along.”

A camaraderie is developing. But when the girls are not practicing or playing together, they might watch the boys’ teams play.

And when Thornton plays Biddeford? “I’ll sit with Thornton,” Atwater said.