One key group that has shaped the debate over overhauling the admissions policy at the prestigious Thomas Jefferson High School for Science and Technology: The Fairfax County Association for the Gifted.

FCAG is a group of parents pushing for a system that would give more weight to math test scores in the admissions process and less to essay-writing — a general approach endorsed by the majority of board members Thursday night.

The heart of FCAG’s argument is that TJ shouldn’t be a school for kids who want to go to the best college-prep school in Fairfax. It should be a place for kids who are passionate at — and really really good at — math, science and technology.

The current admissions process doesn’t reflect that single-minded mission, said FCAG President Grace Chung Becker.

“TJ is not a school focusing on developing a well-rounded kid,” she said. “It’s focused on preparing kids in science, engineering, technology and math.”

Not every TJ parent agrees with that argument, but it resonated with at least several board members Thursday. The admissions process now, said board member Elizabeth Schultz (Springfield) is “not based on science, it’s not based on aptitude, it’s based on what they write — which is a liberal arts approach.”

There is perennial debate over TJ admissions because of the longstanding underrepresentation of some minority groups and more recent concern about the rising number of students who need extra help to keep up with the school’s rigorous academics.

FCAG has buttressed its call for change with an analysis of detailed admissions data retrieved under a Freedom of Information Act request. School board members received a presentation of FCAG’s analysis before Thursday’s meeting, and it’s worth a look [PPT] for anyone interested in how TJ students should be selected.

Among the most counterintuitive findings: Downplaying math test scores may contribute to the continued underrepresentation of some minority groups at TJ.

For example, according to FCAG’s analysis of admissions data for the Class of 2011, 25 Latino students applied to TJ. Of those, 11 were among the total 489 students admitted that year. But three of the rejected Latino students had scored above 45 out of 50 on the math admissions test — a performance that put them in the top 440 applicants based solely on test scores.

The school board on Thursday asked its staff to do further analysis to understand how shifting the weight of various admission criteria would affect diversity. Evan Glazer, the school’s principal, also asked for detailed admissions data so that his staff could look for patterns: Which factors best predict academic success at TJ? Which best predict struggles?

It appeared Thursday evening as if Glazer would get the information he asked for.

(You would think that, as principal, he would already have access to admissions data, but that’s never been the case. There is a longstanding firewall between TJ admissions and TJ school staff.)

One idea endorsed by FCAG is for the county to consider opening a second high-level magnet school to attract kids whose passions are in the humanities.

That argument was floated at the board meeting by member Ryan McElveen, who said he worries that TJ draws too many students who “want to go to the best school in the nation and they might not have the strongest math background.”

Deputy Superintendent Richard Moniuszko agreed.

The admissions process allows for admission to TJ of bright students who are good in math, but “who don’t have that fire in their belly for math science and technology,” he said.

“But they’re being encouraged to go to TJ and that causes a lot of consternation with kids that don’t get in,” Moniuszko added. “In that sense I think, another school that didn’t have a math/science focus might be a better match for some of those kids.”

Most board members Thursday night said they wanted to make more immediate changes. A first round of tweaks to the admissions process could happen this year in time to affect the prospects of rising eighth graders.

Several board members argued that is too fast and the school system needs more time to study possible changes. Megan McLaughlin (Braddock) rejected that argument.

“Teachers have said to us, ‘We’ve seen a very serious pattern here,’ and you all want to sit on your hands for another year?”