Across the expanse of green playing fields, screams hung in the cold morning air.

Happy screams.

"You see? They're having fun," said Bill Kennedy, facilitator for Bethel Park High School's physical education department.

Proving that the "gym" can be taken out of gym class, the school district has been branching out with formerly unheard-of high school programs. Its Eco-Fitness Education Program has students biking, dancing, lifting weights, swimming and -- coming soon to some flat all-sport outdoor courts -- inline skating.

Some of the so-called "lifetime sports" programs were put in place four years ago, but a recent $10,000 grant through the Highmark Healthy High 5 Challenge allowed the district to buy 30 Trek mountain bikes along with helmets and cycling-related equipment.

It also helped buy 26 pairs of inline skates.

Pennsylvania law requires anyone 12 or younger to wear a helmet while riding a bike; in the Bethel Park classes, it's a must.

"The school can mandate [helmets], to stay on the safe side," said Principal Zeb Jansante.

The Highmark grants were awarded to several local schools, including Bethel Park's middle and elementaries, as well as Baldwin High School, which purchased some recumbent bicycles and put other monies toward a nutrition program.

But Bethel Park's program, "for Western Pennsylvania, is unusual," said Sam Kaufman, assistant manager at TRM Cycles in Castle Shannon.

TRM provided the district with a deep discount on the bikes. Trek is among the most respected bike companies in the world, and the 3700 model bought by Bethel Park normally retails for $349 each.

"They've got a pretty cool thing going," Mr. Kaufman said.

The mountain bike classes are held every other day through nine weeks, with off-day alternatives including weightlifting and aerobic dance exercise.

Mr. Kennedy, Lisa Serafin and Myrna Thomas teach the classes. The students generally form groups based on skill and endurance levels, although a few are still beginners.

"Some of these kids hadn't been on a bike since second or third grade," Mr. Kennedy said. "We took them down to that field and they practiced riding in a straight line."

Stressing safety, each small group has one rider assigned to carry a walkie-talkie in case of emergency, and the students must stay with their groups.

"If you break away from each other, you're done," Mr. Kennedy said.

For the most part, students are eager to jump onto their bikes and ride. But first, there were checklists.

Gym classes have 42 minutes of class time, but after getting to their assigned bikes and running through the lists --everything from making sure the brakes worked to checking seat adjustments -- and putting the equipment away later, riding time is half that amount.

Still, it's enough to get a good heart-rate going, especially among some of the guys with BMX experience.

Scott Cramer and Brian Meenan are seniors who figure they can get in three or four miles a class.

"It's fun, and a good workout," Scott said.

"And we've only had one accident," Brian pointed out. "Going down a hill, a kid hit the front brake."

Bethel Park High School sits on 80 somewhat hilly acres, with enough broad fields and driveways closed to vehicles to make the bike trails workable.

Before each class, the red-and-white bikes and corresponding red helmets are lined up on the grass, locked to nearby flag poles by security cable.

About half of Mr. Kennedy's second-period class headed out on the long course

From a quarter-mile away, there were a few whoops and screams as they flew down a grassy slope.

A short while later, more shrieks as another group tackled short but steep inclines close to the school buildings.

"Oh my, it's a caterpillar!" yelled Sam Shaffer, laughing and pointing to something on the road.

She and fellow senior Geri Hayes clearly were not going for mileage, but they were having fun.

"Can we get squeaky horns?" she asked Mr. Kennedy as she walked her bike back at the end of class.

He just smiled.

"When we were young, we came home from school, then you jumped on your bike and rode everywhere. Now, bike riding is kind of a lost art," he said.

"I tell my students we will be out here if it's 40 degrees or higher," Mrs. Serafin said. "It's better than being in the gym and jogging in circles."