Although 16-year-old Lori Montefusco receives a weekly allowance of $10 from her parents, she works about 20 hours a week after school as a sales clerk in a dress shop. Montefusco, a junior at J.E.B. Stuart High School in Fairfax County, said she uses her $65 paycheck to save for college, buy new clothes and pay for recreation.

Wendell Wallace, a junior at Anacostia High School in Washington, said his mother cannot afford to give him an allowance, buy his favorite designer jeans or pay for his dates on weekends. So Wallace, 17, spends 25 hours a week cooking hamburgers at McDonald's, where he earns $170 every two weeks.

Montefusco and Wallace are part of today's large generation of high school students who work -- some simply to help their families make ends meet or to cover their own essential expenses, others to enjoy the clothes, stereos, vacations and motorcycles or cars that their parents will not or cannot provide. Whether it is ultimately beneficial or harmful for the students to work is a sharply debated subject among both educators and parents.

A 1980 survey of 58,000 high school seniors and sophomores by the National Opinion Research Center (NORC) at the University of Chicago found that 65.5 percent of all senior boys and 61.1 percent of the senior girls had jobs. For sophomores, the figures were 44.3 and 40 percent, respectively. While some of the students worked fewer than five hours a week, more than 70 percent worked 15 hours or more, according to the survey. Their total earnings last year were $8.5 billion, according to statistics compiled by the U.S. Labor Department.

Although there are no comprehensive statistics on Washington-area students who find their own jobs, the administrators of school-sponsored "cooperative education" programs, in which students combine classes with paid on-the-job training, say their enrollments generally have increased in recent years.

Nina Gaskins, supervisor of cooperative education programs in the D.C. public schools, said, for example, that enrollment in those programs more than doubled in the last three years, from 882 in 1978 to 1,803 this year.

In Montgomery County, the enrollment in cooperative education grew from 1,852 in 1975 to 2,317 in 1981, while in Prince George's County the enrollment increased from 1,30l to 1,412 over the same five years.

Cooperative education enrollments in Fairfax County increased over a five-year period from 2,622 in 1977 to a current figure of 3,104 students.

Experts divide sharply on the effects of such work on high schoolers: whether they receive lasting benefits beyond the material possessions they acquire, or whether their academic performances will suffer, perhaps increasing the likelihood that they will end up with lower-paying jobs in later life.

"Research has shown that, by-and-large, the effects of high student employment are not good," said Albert Shanker, president of the 600,000-member United Federation of Teachers. "Employment takes valuable time away from their school work, their grades are likely to suffer, and the money they earn is not saved, but often is spent on drugs, alcohol and entertainment."

Shanker's attitude is reflected in a recent survey of 3,100 high school workers by University of California professors Ellen Greenberger and Laurence D. Steinberg.

"We found in our research that youngsters who worked longer hours on their jobs became less and less interested in their school work," Greenberger said. "Working students frequently suffer a drop in their grades and the stress, time pressures and tensions brought on by an unsympathetic boss often lead working students to increased use of alcohol and marijuana."

Although the study, funded by the National Institute of Education, concluded the effects of high school student employment are basically negative, Greenberger acknowledged that part-time work sometimes can provide students a chance to learn "modest lessons" in responsibility, self-reliance and social interaction.

At the other end of the spectrum, the NORC study -- prepared for the National Center for Education Statistics -- found essentially that students who work during their high school years suffer little or no adverse impact on their academic performance.

"We found no major differences in the grade point averages between students who work and those who don't," said Noah Lewin-Epstein, the primary author of the study. "The survey also showed that hours spent at work did not place unusual demands on their time. Students still had time to do home work, watch television or be with friends."

Lewin-Epstein also said some students earn as much as 15 percent of their family's total annual income and learn skills on part-time jobs that later become the basis for careers.

Although many students work because they or their families need the money, some researchers have found that money earned by high school students is more often spent on the "fluff and tinsel" of life than on the essentials.

Michael Borus, director of the Center for Human Resources Research at Ohio State University, said his studies of working high school students showed most of them spend their earnings for "nonsurvival" purposes, with only 5 percent of the students surveyed using their part-time income to supplement their family's budget or to pay their own basic living expenses.

Greenberger of the University of California had similar results. "We found that kids don't invest in their own future and they don't help their families. What they earn is spent primarily for such things as records, cars, televisions, stereo equipment, extra clothes, cigarettes, alcohol, and marijuana."

The ongoing debate is captured in one corridor at Fairfax's J.E.B. Stuart.

Muriel Stubbs, who teaches 11th grade English, said 18 of 22 students in one of her classes have part-time jobs. "I've found that many students who have jobs do not perform well academically," she said. "Some working students tend to be tired all day long. They sometimes do not do their home work, and some fall asleep in class."

"For a lot of working students, the job is their first priority," Stubbs said. "The school cannot compete with the money they earn at work or the kind of independence they can exercise when they're on the job."

Just down the hall from Stubbs' classroom, 12th grade English teacher Ann Peabody said she has found that most of the working students in each of her four classes seem to manage their part-time jobs and school work well.

"Many of the students who work have learned how to plan their time and to organize their life so that they can keep up in their class and work too," Peabody said. "The working students tend to be those who are not planning to attend an Ivy League college. They have entered the job market to buy for themselves the things their parents can't afford to give them."

Stubbs said that Lori Montefusco is an exception to her concern about employed students. "Lori is an exceptionally conscientious student who has managed to maintain a job and her good grades," Stubbs said.

Montefusco, who lives in the Lake Barcroft area, said her parents objected when she told them she wanted to get a job and earn extra money. They feared her 3.3 grade average (4.0 is the highest possible) would be in jeopardy if she worked.

Lori's father, John Montefusco, a retired military officer, now says that part-time work has not hurt his daughter's academic performance. "Lori's done very well," he said. "She's a good student and I think she divides her time well between her school work and her job."

For some students hoping to maintain top grades, a part-time job does not work out.

Christy Nugent, a senior with a 3.8 grade average, aspires to study engineering at an Ivy League school. She said she recently gave up a part-time job in sales at a camera shop after she found that her grades were beginning to drop.

"I was working four hours a day and I didn't have enough time to do my home work," said Nugent, who this semester is taking calculus, drafting, government, journalism and college-level English and chemistry in a high-level academic program at Stuart. "I decided that good grades in my courses were more important than the job."

Wendell Wallace, who eventually would like to be a brick mason, said his part-time job at McDonald's is as important as his performance in school, where he said he has a C average.

When Wallace, a resident of Southeast Washington, started high school, his mother suggested that he get a part-time job to help pay his living expenses. "My mother said she could not afford to buy me all of the things I would want and need for school," Wallace said recently as he stepped briefly away from a grill stacked with steaming burgers. "She wanted me to get the feel of making it in life on my own."

Wallace's mother, Beatrice Mahoney, who is divorced, said that both her son and 18-year-old daughter, Lisa, a freshman at the University of the District of Columbia, work part time and pay virtually all of their personal expenses.

"I feel good about my children working," Mahoney said. "The money they earn pays for their transportation, their recreation and food away from home, their school tuition and fees and their clothes. I would never buy my son designer jeans. But he likes them and buys them with his own money."

When Douglas Bohrer, 17, finishes his classes at Stuart High School at 10:40 a.m., he heads for his job. From noon to 6 p.m. five days a week and all day on Saturdays he repairs electric shavers to earn about $133 a week.

Bohrer, who said he is a C student, plans to attend college, but there are some things he wanted while he was in high school. Currently he said he is saving up for a car. Already he has bought two motorcycles, a truck, and a $1,000 stereo component system with his earnings.

"I just like to be independent," Bohrer said. "I like to pay for my own entertainment. Bar bills can be awfully high these days. You sit down with a friend for a few drinks and end up with a bill for $30."

Greciela Bolognesi's father is a butcher. When she told him she wanted her own car, he told her to get a job and buy it herself. So last month, Bolognesi, also a senior at Stuart, went to work as a cashier at an Italian restaurant in Fairfax County where she works 35 hours a week.

"My father wanted me to get out and see what it is like to work," said Bolognesi, who added that she plans to attend college. "Working is hard. I get about four hours of sleep at night after I do homework for five classes. But I am willing to work to get something I really want."