Jill Martin, a 17-year-old senior at T.C. Williams High School in Alexandria, leaps into her day at 8:20 a.m. when her first class begins. By 1 p.m. she is working at a nearby Baskin-Robbins ice cream store where she manages a half-dozen other high school student workers. It is not until late in the evening that she is home and free to tackle homework for the next day.

"It's really a hassle some days," said Martin, who works 35 hours a week at the ice cream shop, in addition to being a cheerleader and president of a jobs club at school. "But it's definitely worth it: the money, the experience."

If the 1970s was the decade of the supermoms, then perhaps the 1980s is that of the superkids: those increasingly numerous students who juggle school, job and extracurricular activities as well.

Experts say more high school students are working than ever before: An estimated 30.5 million, or one-third of all high school students, work part time. Local guidance counselors estimate the figure in Northern Virginia is much higher, perhaps more than half of all students.

Many of these teen-agers need the money from part-time jobs to help out the family budget or save for the ever-escalating cost of college. But counselors say many students from wealthier areas work to support life styles that include cars, clothes, stereos, movies and dinners out with friends.

It is not always a desirable situation, however. One study recently released by the government found that teen-agers who work are more likely to get in trouble with the law than those who do not.

Some area teachers, counselors and coaches also complain that working students have little time for homework and after-school activities. They say the grades of a student who works often suffer.

"They're more interested in clothes and cars now than academics," said a teacher at Arlington's Washington and Lee High School who asked not to be identified. "I can sympathize with the ones who really do have to work, the children of immigrants mostly.

"But the others work for material goods. They are always tired, never do their homework, can never come for extra help after class. Ten years ago, you would never have seen this."

Local educators are not alone in their concern. The state Board of Education is considering a policy that would require high school students to remain in school for the entire day.

Students such as Martin who leave school early to work for vocational education credit would not be affected by the move. But other students would have to prove to local superintendents they need to work before they could be excused early.

"We are after the students who don't really have to work," said state Superintendent of Schools S. John Davis. "Public education has a lot to offer these students."

Not surprisingly, many educators say working teens do not suffer but gain from the responsibility and time management they learn from jobs. Martin noted: "Kids who are not going to do their homework will find an excuse not to do it, job or no job."

"There is no evidence to show that students who work are less academically inclined than students who don't work," said Jim Hill, director of guidance at Washington and Lee. "We require our students to be in class all day unless they have a note from their employer. We've had no problems."

Ruth Blair, a job counselor who helps T.C. Williams students find work, said more and more students are interested in finding part-time employment.

"It is becoming a very accepted and desirable thing to have an after-school job," Blair said. "There are a lot of traditional student jobs in the area: fast food and stores. The students make minimum wage and are happy. Most kids tell me they want to work because they hate to ask their parents for money. Their parents encourage them to work."

But the parents of T.C. Williams senior Bill Dixon, who works with Martin at Baskin-Robbins after school and a few hours on Sunday, hold the opposite view. Last spring, they increased his allowance so he would not work and would concentrate on his studies instead.

"They thought I should spend more time on my studies and were willing to pay for it," he said.

His grades improved slightly, he said, and this fall he went back to work because he liked having his own money to buy lunch at Roy Rogers and a movie Saturday nights.

"I'm wiped out at night and my homework doesn't always get done," said Dixon, 17, who takes all honors classes and is a member of the student government and debate club.

He said many students join extracurricular activities and hold jobs because it looks good on college admission applications, although it can be "an incredible drag at times."

Of course, not all students work. Dixon's friend and schoolmate Sam Baker has opted not to hold an outside job.

"I work at sports after school until 6 or 7 o'clock at night," said Baker, 17, an honors student and editor of the student newspaper. "My parents would rather see me concentrate on my classes so I get into a good school. But there are other kids who have to work either because their families are poor or because they want to have nice things.

"There is definitely some pressure among groups of students to dress nice or have your own car."

At Falls Church High School, swimming and assistant football Coach John Totten said not all students are like Baker, willing to forgo work for sports.

"There are some good athletes walking around this school that we never see because they probably work and don't go out for sports," said Totten, who has been coaching on the high school level for seven years. "We have to schedule practice around everyone's work schedule, and it gets harder and harder.

"I think these kids who work are good kids," he said. "But they're certainly missing something somewhere."