The five engineers on the winning team in the nationwide design competition were celebrating their victory, partying hard on Haagen-Dazs and Nestle bars in their top-floor headquarters, standing around the soaring creation that had absorbed so much of their time and imagination, and boasting that no one else could have done the job.

"Especially not boys; boys are too picky," said 12-year-old Melissa Rivera. Boys want everything their own way, Melissa said, and they don't make good team players. Girls, simply put, can do just as well, maybe even better, she said.

That brimming confidence is part of the reason five girls won the Erector Set Contest. That's right: Erector Set, the model-building package of nuts, bolts and miniature girders that were supposedly captivating only boys since it was introduced 80 years ago; the same toy that used to be marketed to "boy engineers."

On Thursday afternoon, the girls were proudly showing off a "Diploma of Merit" signed in official-looking, illegible flourishes by officials from Meccano, the French toy company that reintroduced Erector Set in 1991, after buying the rights from the A. C. Gilbert Company, the founder.

Inspired by Toothpicks
The diploma was issued to the Civil Engineering Club of Public School 147, comprised of the five girls until June, when they graduated from the elementary school, at 325 Bushwick Avenue in Bedford-Stuyvesant, Brooklyn, and moved on to intermediate school.

Their winning entry was a six-foot-long suspension bridge with a span of about four feet, an impressive creation considering that the longest girder in the kit is about a foot long. The idea for the arch that bears much of the weight came from a book the girls got from a teacher on how to build a bridge from toothpicks. From there they improvised. They added vertical load-bearing girders and then a second arch of girders under the roadway.

They were vague, perhaps deliberately, about precisely who did what in the design and construction.
"We don't really remember," said Jean Ng, the class valedictorian. "Everyone put in ideas, and we used all the ideas."

"One person cannot take credit for the whole big bridge," Melissa said.

No Boys Allowed
The engineering club has no boys for a reason, said Norman Scott, adviser to the club, which meets every Friday from 3 to 5 P.M. "The minute boys are around, the boy-girl thing starts, and the performance of girls drops drastically," he said.

Mr. Scott, who has been at P.S. 147 for 23 years and taught sixth grade for most of that time, said that when boys are present, girls start deferring to them. But a bigger problem, he said, is that when boys are around, girls tend to intimidate other girls who act assertively.

Recent research has shown that girls often perform worse on standardized tests for math and science, subjects in which boys tend to dominate classroom discussion. In response, three California schools are segregating girls in some classes to try to improve their performance in these areas.

The girls offered their own explanations for their approaches to these subjects, saying that they have attributes the boys do not. "Some boys, they can be so lazy," said Bonnie Resto. "You think the boys would stand up long enough to build this?" she asked, pointing to the arch.

The arch involved some trial and error, Mr. Scott said. He told them to stretch it apart until it began to sag, and then to build the rest under it.

Last year, Mr. Scott and another teacher at the school, Mary Hoffman, received a $500 grant from the Fund for New York City Public Education, a charitable group, and spent most of it on Erector Sets, which the toy maker provided at the wholesale price. Mr. Scott said he had always wanted one as a child and still thought of them as educational. In June, the company mailed him an announcement about the contest.

A Tradition Revived
Erector Set contests began in 1914 and drew thousands of entries, but A. C. Gilbert later dropped them. Meccano revived the contest this spring, asking people to send pictures of models built with Erector Sets. According to Meccano, among the thousands of entries this year was an elaborate moving model of Mickey Mouse from two Walt Disney Company employees , and an 18th-century ship . Bill Rush, 10, of Pleasant View, Utah, sent a photo of his sculpture of his mother, who is blind, and her seeing-eye dog.

The four categories were junior, advanced, adult and school; the girls won in the last category after sending in photos of their creation. Their bridge, which used most of three Erector Sets, was already famous locally; they showed it off at graduation last spring. Now they have all turned 12 and are in seventh grade, but they still return to visit Mr. Scott, whose fifth-floor classroom is jammed with computers. A corner has boxes of Erector equipment, which he calls his "parts department."

Their $1,500 prize will go to their alma mater. "I want the money used for this room," said Ivonne Miranda, who, along with her four partners, wants to add a new computer to the classroom. The fifth member of the team, her twin sister, Shavonne, said the award should not only cover the price of the computer, but also "the plaque with our names."

Photo: A team of five girls from an intermediate school in Bedford-Stuyvesant, Brooklyn, are the winners of this year's Erector Set Contest. Standing around their winning creation, a six-foot-long suspension bridge, were, from left, Ivonne and Shavonne Miranda, Jean Ng, Melissa Rivera and Bonnie Resto. (Rebecca Cooney for The New York Times)