The lights in the sawdust-coated gym go out dramatically. To the whir of drills and clank of saws, a construction worker on a cherry picker flashes an overhead and projects a 16-foot-tall outline of a cougar head on the wall.

John Burley, principal of this brand-spanking-new Forest Oak Middle School in Gaithersburg, one of eight new Montgomery County schools being built or totally modernized this summer, is silent.

"You said you didn't want a fierce cougar," architect Ivor Carrington said worriedly of the about-to-be-painted school mascot. "We gave you a gentle cougar."

Burley, clad in T-shirt, shorts and sandals, considers the wary-looking beast and asks if the ear will stick up into the yellow stripe near the ceiling and the whiskers will intrude upon the white below. Once assured it will be centered, he gives his blessing and moves to the next project: finding out why the painter hasn't begun to stripe the parking spaces in the just-steamrollered asphalt lot out front.

"We will be ready for school," he said firmly. It starts Sept. 1.

Burley should know. This is the third new school he has opened in Montgomery County in the past decade. His track record exemplifies the rapid growth in the county, as birth rates climb and new housing units spring up like mushrooms, as many as 4,500 a year, and young families drawn to the county's reputation for excellent schools move in.

Still, despite this year's record summer construction in a 10-year building boom, the county's schools are bursting at the seams. Forest Oak will open its doors to 935 students in less than two weeks and nearly reach full capacity. The influx of 3,000 students this fall, which will boost enrollment at the county's 185 schools to about 131,000, reflects a trend that is expected to continue over the next few years.

And, with the baby boomlet peak of 12,000 births in 1990--enough to fill a classroom a day for a year--reaching third and fourth grades, the pressure is on to find more room in the county's already tight middle schools.

To handle the burgeoning enrollment this fall, the county must use 50 more portable classrooms than last year, bringing the total to 286.

"We keep growing," said Richard Hawes, director of construction and facilities for Montgomery County's schools, "beyond people's wildest expectations."

Hawes spoke between bursts of cell phone rings and walkie-talkie chatter, troubleshooting everything from plumbing problems to eager teachers wanting to get into classrooms still littered with boxes, nails, two-by-fours and other construction detritus.

This summer, Hawes is overseeing what the county calls one of the most "ambitious capital improvement efforts in the school system's history."

The biggest projects include the building of Forest Oak and--among other roof repairs, classroom additions and air conditioning projects--the total gutting and refurbishment of the once dark and dank Kennedy High School.

The former North Bethesda Junior High was one of 65 county public schools closed or leased in the baby bust of the 1970s and early 1980s; total school population in the county plummeted to around 91,000 in 1983. It, too, is being modernized this summer and will reopen as North Bethesda Middle School.

And the former Blair High School is being renovated and will reopen as two schools, Silver Spring International Middle School and Sligo Creek Elementary School, sharing a building.

"All told, the new projects will total around $140 million," Hawes said as he pulled up to Kennedy High School in Wheaton. Outside, cheerleader hopefuls kicked and pompommed on the new front steps as an acrid vat of roof tar baked in the summer heat.

Kennedy and the other schools were scheduled for modernization based on the age of the building, the number of outstanding work orders and requests for maintenance and an independent assessment by a consultant. The result has been a school-by-school priority schedule that people can lobby to accelerate, but no one can change.

"There's a lot of pressure on the board to move the priorities around," said Joe Lavorgna, director of planning. "But the process, ranking the schools very objectively, takes a lot of politicizing out of who goes first, second, third and so on."

Kennedy, its old stucco facing replaced with a sleek brick facade, is a building that has weathered the shifting whims of educational theory and societal concerns.

It was built in 1965 as an "open school," then the latest rage of that experimental era. Its classrooms were barn-size. Students chose their own teachers and had eight minutes to change classes while their favorite rock groups blared over the PA system.

"It was pretty freewheeling," said Kennedy business manager Trish Toven. "It became apparent fairly quickly that that wasn't working."

With too many students lost or distracted in the shuffle of open schools, Kennedy, like others across the nation of its era, put up walls. The result at Kennedy, Toven said, was a hodgepodge of odd nooks and crannies and tiny classrooms with no windows. The energy crisis of the era also cut way back on what officials saw as heat wasters: windows. So buildings of the 1970s are, by code, dark and stuffy.

But those hot boxes made for poor ventilation and created air quality problems. So the latest building codes allow for energy-efficient glazed windows. And now that Kennedy has been stripped to its structural supports and rebuilt, with skylights and big windows, it is light and airy. "It's a completely different place," Toven said.

For Hawes, the biggest problems with the school had more to do with the latest societal concerns: safety and security. No one knew which entrance was the main one. No one knew where the main office was. And usually, it was buried deep inside the building, where staff members had no clue nor control over who was coming and going.

Now the main entrance is set apart from others with an arch and a prominent set of stairs. The bus loop is separated from the car loop, so students getting off buses won't be forced to weave between students parking or parents dropping students off. Most important, the main office is clearly the first thing you see in the airy terrazzo-floored lobby. And a long bank of windows to the outside ensures that administrators can clearly monitor the front entrance and be the first to spot signs of trouble.

Classrooms are now designed to be flexible, Hawes said, pointing to a computer station along one wall and areas for small group work, because teachers no longer just stand at the front of the room and lecture. The "Media Center"--called a library before it was stocked with videos, CD-ROMs and cassettes as well as books--is now at the core of the building instead of stashed away. And noisy areas, such as the gym, auditorium and music rooms, have been separated from the quiet academic areas.

"Schools are now being used as community centers, for school-based health centers and for after-hours programs, and we built these areas so they can be completely separated from the main school," Hawes said, echoing a theme pushed by U.S. Secretary of Education Richard W. Riley. "The designs have evolved to respond to the latest issues in society."

Back at Forest Oak Middle School, Principal Burley, struggling to be heard over the rhythmic zizzing of handsaws and the whine of an industrial vacuum, said societal concern and philosophy have shaped the design of his school as well.

"Socially, emotionally, psychologically, kids change enormously between the ages of 10 and 13. And parents are usually worried about the transition from elementary school, where they had one teacher, to middle school. They say, 'Oh, my child is going to get lost, he'll have so many teachers,' " Burley said. "But we've designed the school and the program instruction for kids to feel safe. We want them to be in a school with 900 students and still feel like it's a small place of their own. That's important."

To do that, students are divided into sections of about 130 students. Each section goes to class primarily along one hallway. In that hallway, a team of teachers teaches the same students, from English and social studies to math and science, to better get to know students and to share information about their progress, Burley said.

But while Burley marvels at his 40-acre, "spectacular" new school, Don Barron, principal of Montgomery Village Middle School, bemoans his old one.

When you walk in, past the 1960s-Frank Lloyd Wright-esque pavilion with chipped paint, you first notice that you have no idea where the main office is. Wander to the left and you find a door mysteriously marked "GOF" next to another labeled "COU" and assume the general office is next to the counseling center. The next thing you notice is that it's hot.

"We're bursting at the seams," Barron said as he strolled down an un-air-conditioned hallway called Success Avenue with questionable fluorescent lighting fixtures.

"The tiles are asbestos, which means we can't touch them. The boilers are on their last legs; they're basically held together with duct tape and glue. We're not handicapped accessible. And the design just doesn't work for the new philosophy of middle school."

And Barron is one of the lucky ones. Although the county promises to consider each building for modernization once it hits the 30-year mark, it is far behind schedule. More than 60 schools fill the construction calendar until the year 2017. And 45 haven't even been assessed.

Montgomery Village, Barron noted with relief, is next on the list.