John Dean paced in the front of the auditorium, microphone in hand, looking out over an audience of eager faces.

"Now," he said, "should we do one slide or more than one?"

Dean cupped a hand to an ear and listened to his crowd, about 100 squirming elementary school students sitting cross-legged on the floor.

"More than one!" they screamed in unison.

"Okay, okay. So we might have a slide that goes like this," Dean said, making a fluttering, whistling noise and spiraling his finger downward.

"Or we might have one that goes like this," he said, waving his hand over imaginary bumps and spitting out a "thump, thump, thump" noise.

The children giggled, transfixed.

This was exactly what parents at Sully Elementary School in Sterling were hoping for when they hired a specialty firm based in Ithaca, N.Y., to design a playground they've dubbed Discovery Park. Dean spent several hours at the school Tuesday, listening to children's ideas, which included trampolines, towers and tree houses.

Then he sat at a table on the school's brightly lit stage, drawing out their ideas by hand. Children were brought up slowly to watch him work.

"This is done with a pencil, not a computer," said Dean, a former drummer and "normal architect" who has spent the past 20 years designing playgrounds. "The kids get to see the process. They'll see me scribble. By the end of the day, I'll have a beautifully rendered design, but it won't start that way."

Loudoun schools come equipped with only a simple set of monkey bars. Schools that want more -- and most do -- must raise the money and arrange the improvements themselves. It's a time-consuming and community-building process undertaken by schools across the county in recent years.

Parents at Sully, which is nearly 40 years old, had been talking for years about mounting such an effort. But they learned last spring that such efforts have typically brought in $40,000 to $50,000.

"If we're already raising that much, why not just go for more?" said Valerie Petrey, who has two children at the school and is co-chairman of the project. Parents have held several fundraising events recently to get the ball rolling.

Instead of building just a playground, they decided to build a kind of science park that can be used for play and will be connected to classroom studies. They've expanded the idea to other educational topics, including history, music and math. And they wanted something custom-built, not a catalogue item. In all, they estimate, their playground will cost $100,000.

Petrey and her playground partner, Peter Kronenberg, who has a third-grader at Sully, have been forwarding to Dean ideas that they have seen at science museums and from playgrounds across the country that they have found on the Internet. They have already decided that their playground is likely to have weather stations, a math maze and, at the request of a fourth-grade social studies teacher, a Jamestown fort.

"We want something more than just a regular playground," Kronenberg said. "It's a playground, but it's got a lot of educational aspects to it, things the kids can do and learn at the same time."

Raising the money, they acknowledge, will be particularly difficult at Sully, where more than half of the students receive free or reduced-price lunches, a common indicator of low income.

The PTA has applied for a federal neighborhood revitalization grant. It is also hoping for donations from local businesses. If those efforts are successful, Kronenberg said, hundreds of volunteers will be needed to build the playground next October.

Sully is in the heart of Sterling Park, and Principal Clark Bowers said the playground will serve an especially important role in the changing community, home to many recent immigrants. Most students live within walking distance of the school, and there are few other playgrounds in the area. He said the playground will be a place for parents and children of all backgrounds to come together, even after school.

"One of the things that just has to continue to happen is that people have to get together and talk," Bowers said. "The playground, the basketball courts -- they offer our community a place to talk and find out the differences between them are not that big. They get to meet each other's kids. They'll learn about the school there."

Bowers said that Sully, like many schools, has trouble getting immigrant parents, who often hold two or three jobs, to be involved at school. Many also come from countries where parents are not encouraged to visit their children's schools.

He said the playground project could be a bridge, allowing parents to use their skills to help the school, so that they become more comfortable there.

"Hopefully, they'll feel like they have a stake in this school and say, 'Hey, I built this,' " Bowers said.

To help the effort, all playground fliers are being translated into Spanish. Clivia Velasquez, who works as the school's liaison with parents, has promised to do whatever she can to reach out to non-English-speaking parents, from making cajoling phone calls to paying visits to their homes.

"We're going to do whatever we have to do," she said. "Sometimes parents will say, 'I don't have anyone to watch my kids.' If I have to baby-sit those kids, I'll do it. . . . If we have to go and get someone from the house and they need a ride, we can do that."

At their meeting with Dean, the children needed no convincing.

"Are you going to help me build this playground?" he asked.

"Yeeesss!" they shouted.

At a PTA meeting Tuesday, architect John Dean with the playground design firm Leathers & Associates unveiled a sketch of the new playground planned for Sully Elementary School.John Dean, a designer with the playground design firm Leathers & Associates, gives a slide show to the school's PTA showing some examples of other playgrounds he has designed across the country.