WASHINGTON (AP) _ Joseph Taylor recalls with laughter the homemade thermostat he made for a fourth-grade science fair project. ''It wasn't a very good piece of work and it didn't win any prizes.''

Still, he enjoyed making it. ''You usually have fun doing things that you're good at,'' said Taylor. And he won a prize for his later work: the 1993 Nobel Prize in physics.

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In schools across America, it's science fair season - gyms filled with volcanoes erupting, plastic hearts pumping and magnets lifting and pulling. The projects range from simple and homemade to complex and unpronounceable.

Some school districts are moving away from the competitive nature of the fairs, saying it takes the fun out of discovery. Others believe students thrive when vying for prizes from trophies to scholarships.

Just last week, the nation's premier science fair, the Westinghouse Science Talent Search awarded $205,000 in scholarships to 40 students.

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Science teachers say students do better on projects exploring subjects they are interested in.

For her entry to the fair in Fairfax County, Va., musician Jennifer Dilling set out to determine whether there was an underlying mathematical structure to music. Using a supercomputer, she concluded there was.

Think of the possibilities, like finishing Schubert's Unfinished Symphony, said Dilling, who plays the trumpet and piano.

She won a first place in the mathematical category.

Tyler Brickner, 15, turned a personal calamity into a science fair project for two straight years. After breaking his leg while playing soccer 15 months ago, Brickner looked at effectiveness of different shinguards for the 1993 science fair. This year, he tested different components of shinguards to develop a better one.

He took second place in engineering.

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Joan Goodman, a science teacher at Los Lunas Elementary School in Los Lunas, N.M., said children weren't learning from traditional science fairs because ''all you're doing is judging what the parents can do.''

Ellen Mayo, who teaches science at Douglas Freeman High School in Richmond, Va., said she found that when children focused on the competition they had no real understanding of what they were doing in science.

But throwing out the competition doesn't necessarily mean doing away with the projects.

Some schools call them discovery fairs; others, invention conventions.

Students at Wickliffe High School in Wickliffe, Ohio, do research projects and set up an exhibition but ''there is no competition involved at all,'' said Richard Benz, chairman of the school's science department.

This examination of the science fair's role takes place as the nation debates new education goals designed to create world-class standards and make U.S. students No. 1 in math and science by 2000.

F. James Rutherford, director of Project 2061 for the American Association for the Advancement of Science, said science fairs can be an important motivational tool.

''The kids get engrossed, putting together the elements of a contest and a design,'' he said. ''But many times when you look at what the kids actually do, you realize that somehow or other the science actually get lost.''

They'll learn more if schools allow the students to explain their projects to one another, he said.

Project 2061, which produced guidelines for what children should know and be able to do in math, science and technology by the end of grades 2, 5, 8 and 12, is working on a book to help teachers develop curriculum to accomplish those goals.

Among the things it will address, Rutherford said, is ''how can the virtues of science fairs be pulled on to contribute to the serious learnings of science and math and technology.''

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For Brian Rosman, the contribution is the contest.

''The competition gives you a deadline and makes you get things done,'' said Rosman, 18, who this year built a chemical heat pump for the regional Fairfax County fair.

Rosman also says he's learned about different scientific disciplines working on various science fair projects over the years. He plans to major in chemistry at the University of Virginia after graduating from Thomas Edison High School this spring, then pursue careers in medicine and politics.

''The issues before Congress are getting more and more technical,'' he explained.