Tony Bravo, a senior at Centennial High School in Howard County, was surprised last week when his name appeared on the list of National Merit Scholarship semifinalists. The 17-year-old, who is also a semifinalist for a National Achievement Scholarship for Outstanding Negro Students, had not spent much time over the summer wondering how he placed in the competition because he was busy running his own lawn care business.

Ryan Page, a senior at Frederick Douglass High School in southern Prince George's County, was pretty sure he'd made it to the semifinals. After all, if high test scores and a plethora of interests were what educators looked for, he reasoned, a 17-year-old who favors music from the baroque period and political discussions via computer couldn't lose.

Page and Bravo are among the 336 Maryland high school students whose Preliminary Scholastic Aptitude Test scores have propelled them into the semifinals of the Merit competition. The 15,000 semifinalists nationwide will compete for $25 million in scholarships.

"Hopefully I'll get some scholarship money out of this, since the colleges I applied to are pretty expensive," said Bravo, who hopes to attend Massachusetts Institute of Technology or the University of Virginia.

Montgomery County, which has just 14.3 percent of the state's public school students, led the state in Merit scholarship semifinalists with 44.7 percent of the state total.

"Participation in this program is almost a tradition," said Brian Porter, spokesman for Montgomery County schools.

The county also has courses designed to prepare high school students for the PSAT, typically taken in the winter and spring.

Contrary to the stereotype of a monotone student able to recite calculus equations without missing a beat -- though many of these students can do that as well -- this group represents competitive, articulate youths with diverse interests, the least of which is homework.

Ezra and Justin Miller, 17-year-old twins at Bethesda-Chevy Chase High School in Montgomery County, did not take any courses to prepare for the test. That would have gone against the two seniors' belief in taking home as little schoolwork as possible.

"I guess I'm kind of embarrassed to say my study habits are nonexistent," Justin said.

Marc Cohen, a semifinalist and senior at Walt Whitman High School in Bethesda, has a similar outlook. "I take the weekend to relax and wind down," he said. "Unless I have a major project that is due the following week, I don't spend much time studying until Sunday."

Cohen's method works. The 17-year-old is able to keep a 3.7 grade point average while involved in student government and volunteering with the Montgomery County Special Olympics as a sports coach.

For Jonathan Holden, a senior at Annapolis High School in Anne Arundel County, placing in the semifinals was just another step toward admission to the Air Force Academy in Colorado Springs and becoming a pilot. Holden, a center on the school basketball team, carries a 3.65 grade point average and holds a part-time job.

Prince George's County saw its number of semifinalists increase by two this year, to 20. Kate Weizel, a senior at Central High and that school's sole semifinalist, attributed her academic success to attending the county's magnet schools since seventh grade. She is enrolled in Central's Humanities and International Studies magnet program.

A shy student who spent her freshman year making low grades and not many friends, Weizel, 17, joined the pompom squad and finished her sophomore year with a 4.0 grade point average. Now an honor student and member of the cheering squad, Weizel feels she has already reached many of her goals.

"Becoming a semifinalist means to me that if you study and you put your mind to it, you can do almost anything," she said. "It's not that it has changed my life or anything, but it does make me feel good about myself."

Weizel said her parents, who are both defense research analysts, hope academic recognition of this sort will help pay her way through Valparaiso College, a small Lutheran school where Weizel plans to study education.

Howard County, which has 4.1 percent of the state's enrollment, has 12.1 percent of the semifinalists in the state.

Megan Daily, a classmate of Bravo's at Centennial High, doesn't think it was enough that she scored high on the test and has good grades. Daily believes Merit judges looked at her myriad of hobbies, including cheerleading, track, women's lacrosse, theater and a volunteer job tutoring third- and fourth-graders.

"You definitely have to be a well-rounded person to be chosen as a semifinalist," she said. Daily was also chosen as a Maryland Distinguished Scholar in the Arts for 1990-91.

All of which makes Sylvia Pattillo, Centennial's principal, a happy educator: "I'm extremely impressed by their accomplishments, and we're just glad we had a chance to be a part of this with them."