Seventy eighth-graders attended night tutoring sessions in McLean, where their parents paid $30 an hour to a Stanford-educated scientist who drilled the kids on college entrance exam questions. More than two dozen others attended a private learning center in Burke for test practice and admissions counseling -- even advice on elementary school extracurricular activities. Still others enrolled in a certain middle school. All hoped to propel their admission into the elite Thomas Jefferson High School for Science and Technology.

The mammoth -- and costly -- effort culminates this morning, when a record 2,884 Northern Virginia students plan to take the admissions test for one of the nation's most selective public high schools. The Fairfax County school becomes choosier every year: Only 420 students will be admitted next year, and its 15 percent acceptance rate makes it as selective as Princeton and twice as exclusive as the University of Virginia.

The competition has fueled an intense admissions process and inspired a number of ways that parents and students try to get a leg up. A small industry is developing to support students yearning to be part of the select few.

"There is the belief, the perception, that in order to get into an elite college, you have to get into an elite high school, like Jefferson," said Ed Rothschild, whose daughter graduated from the school. "Plus, Jefferson is a public school. You don't have to pay for it."

Maryland and the District of Columbia also have competitive magnet schools, but Jefferson is the highest-achieving school in a region of many, a bridge from gifted classes in the lower grades to the most prestigious colleges and universities, and onward to a successful life.

"This certainly is reflective of the fact that Jefferson has become this elite institution," Fairfax Superintendent Daniel A. Domenech said. "Families go through incredible behavior just to try to get their kids into Jefferson by moving into a particular area or renting a town house near Longfellow [Middle School] or others that they think will give them an edge."

The frenzy highlights a current districtwide controversy about the admission process. Domenech wants to increase the number of students attending Jefferson from less affluent areas of the county, but a majority on the School Board are set to vote against his plan at Thursday's meeting and to endorse a plan to enlarge the freshman class to 420 students instead.

Most of Jefferson's students are from Fairfax County, but Loudoun, Arlington, Fauquier and Prince William counties and Falls Church are also represented. The 120 multiple-choice questions on the admissions test have never been made public; 70 of the questions are in verbal subjects, and 50 are in math.

For the first time, applicants who registered to take the test this year were given a 16-page booklet with test-taking strategies and sample questions.

"We knew that kids were getting help," said admissions coordinator Christel G. Payne, "and it just wasn't fair that a great deal knew what they were facing when they went in on Saturday morning and others would go in cold with no idea what they would be looking at."

Next year, Domenech said, the Fairfax Education Association will spend $85,000 on a preparation course for minority and economically disadvantaged students.

Montgomery County offers a public math and science magnet program within Montgomery Blair High School in Silver Spring. It is much smaller than Jefferson's but just as selective. About 800 students apply each year for 100 spots. Eileen Steinkraus, the magnet coordinator, said applicants used to take the Preliminary SAT, but so many students studied for the test that they abolished it four years ago and had a testing service develop a test for them.

The demand for Jefferson belies a recent national study that found that attending a selective high school can hurt a student's chances of getting into an elite college. Those students generally have lower grades and class standings than they would have if they had attended their neighborhood school.

In McLean, the 70 young test-takers sought help from Tripathi Learning and Enrichment, a tutoring service run by Vijay Tripathi, a Stanford University-educated scientist formerly with the Department of Energy. Two of his five children graduated from Jefferson and his youngest son is among the eighth-graders taking the test today. Last year, he helped 30 students prepare, fewer than half the number who signed up this year.

The Korean community often turns to Jae-Il Scholastic Consulting Services in Burke. Wonjin Lee, the director of education at Jae-Il, said the center is for anyone but attracts Korean families who, because of language and cultural barriers, have difficulty navigating the admissions process. He declined to say how much he charges but says he offers free essay-writing help and general admissions counseling for Jefferson, private high schools in the area and colleges.

Even students who didn't get help outside of school acknowledge buying SAT test guides.

"I look at the SAT book every weekend, and last weekend my mom told me to write an essay," said E.B. Kuhn, 14, who attends Longfellow Middle School in McLean. Jefferson is the next stop on her path to becoming a brain surgeon, she said.

Longfellow is one of several Fairfax middle schools that send dozens of students to Jefferson each year. Today, about 150 of its eighth-graders will take the admissions test. Part of the school's success, some say, is the so-called Vern Williams guarantee, in honor of a longtime math teacher known for his high standards. He also writes about 50 recommendations for Jefferson applicants every year.

"We don't prepare these students to get into TJ," Williams said. "I prepare my students to love learning."

Williams's students acknowledge that his daily lessons are so challenging that the math practice test questions they received from Jefferson were a snap to compute.

"It was ridiculous. It was like sixth-grade stuff," said Alex Smith, 13. "I thought, if this is what the TJ test is going to be like, then I'm not that worried."

Educator Vijay Tripathi helps prepare eighth-graders for the Thomas Jefferson High School for Science and Technology admissions test.The families of Meaghan Allard, left, Tejal Patel, Malavika Vijay and dozens of others in Northern Virginia pay $30 an hour to enroll in the admissions test preparation classes.