Sarah Christian tutors younger students twice a week, helps out at her parents' nonprofit organization, started a conservation club at school, leads children's summer nature camps and, in years past, has sold her homemade peanut butter dog treats to help preserve the leafy Bull Run Mountains near her home in The Plains.

But lest you think the junior at Battlefield High School in nearby Prince William County is simply stacking her resume for college applications, consider this: Sarah says she hates school, with all of its testing and "process." She has no idea where she wants to go to college or what she wants to study. She hasn't the vaguest idea what she wants to be when she grows up.

Instead, Sarah says, her service is totally self-motivated, the legacy of growing up in the Fauquier County countryside surrounded by people passionate about protecting the land. Nevertheless, others are noticing her good work: Last month, the teenager was one of six volunteers nationally recognized for their environmental contributions, landing a $20,000 donation for the Bull Run Mountains Conservancy.

"She's different than most 15-year-olds -- just ahead of her time," said Michael Kieffer, executive director of BRMC, which will receive the check from Recreational Equipment Inc., the sponsor of the award. Sarah, who recently turned 16, has "a kind of maturity about life and situations," Kieffer said.

Indeed, Sarah speaks with striking sophistication. Thanks to lessons from Kieffer, she also talks like a conservation veteran, referring to neighboring Prince William County's "very, very aggressive development policy" and explaining that education, policy and land acquisition are the trilogy of conservation.

"I'm able to help with two of them, but policy is just not something a 16-year-old with no law background can do. . . . I'm doing what I can do," she said.

Sarah's work for the group began with an adolescent obsession with baking brownies and cookies three summers ago. Hoping to channel that energy, her mother, Rita Fenwick, suggested that she sell her goods in the green barns of The Plains' farmers market and donate the proceeds. At first, Sarah gave the $100 she made each weekend to the Middleburg Humane Foundation -- hence the dog biscuits. But when Kieffer became a family friend, she chose BRMC, which is based in Broad Run.

One thing led to another. Soon Sarah was helping in the BRMC office, volunteering at its summer camps and Halloween walk in the woods, and she conducted research on moths and rattlesnakes on the mountain. Kieffer estimates that Sarah has given 200 to 500 hours of her time annually over the past three years.

She founded a conservation club at the Wakefield School, a private school in The Plains that she attended until this year. The club led recycling projects and built bat houses and birdhouses to put up on campus. It wasn't easy: The club had eight members at best, Sarah said.

"Most people either don't do any charity work, or when they do charity, it's their parents forcing them," she said.

Sarah, on the other hand, was taught early to cherish the outdoors by her mother and her stepfather, George Fenwick, who founded and run the American Bird Conservancy, which has offices in Washington and The Plains. They often took Sarah and her siblings -- Rachel, 14, and Cyrus, 12 -- on bird-watching treks.

Sarah did not take much to birds, she said, but did pick up a keen sense of observation and a passion for plants. Ask her what she does for fun, and there is no mention of shopping, instant messaging or other typical teenage activities. Sarah said she prefers chopping wood and raking leaves at the family's 100-year-old farmhouse.

Sarah also credits her mother and stepfather with instilling in her an appreciation for how the "little stuff," such as turning off lights and promptly closing the refrigerator door, can make a difference. And their steady emphasis on helping others stuck, too, she said.

"It's fulfilling to spend an hour making someone feel nice," she said.

Employees at the REI store in Baileys Crossroads asked Kieffer to nominate one of his 50 regular volunteers for the company's Stewards for the Environment award. He said Sarah was the first person who came to mind. She tried to talk him out of it.

"I didn't think I had a chance. I just didn't recognize myself as that much better than everyone else," Sarah said. "He said, 'Look at it this way: If you win, you will be the best volunteer.' " (To say the least: $20,000 is about one-seventh of BRMC's annual budget, Kieffer said.)

Sarah was the youngest nominee and winner in the contest's three-year history, and the judges were wowed, said David Jayo, REI's corporate giving manager. More than 200 volunteers were nominated, he said.

"Definitely, her age made her stand out, but there are a number of factors or criteria that we're looking at," Jayo said. "And she's no less of a hero than any of the other individuals."

Sarah has worked out a way to bring the mountain into her schoolwork, making her studies a bit more bearable. For her science fair project this year, she is planning to compare the presence of macroinvertebrates, such as caddis flies, in two segments of a mountain stream -- one near heavy construction and one in a pristine spot.

As for the $500 gift certificate REI gave her, Sarah has a simple wish. She wants something to help her enjoy the winter cold outdoors: new gloves.

Sarah Christian, one of six national winners of REI Stewards for the Environment awards, collects specimens in the Bull Run Mountains near her home."I'm doing what I can do," Sarah Christian says of her preservation efforts.