IN SOME WAYS, Margaret Murphy, a divorced mother of six on welfare, is a success story. When her youngest child started kindergarten in fall 1987, Murphy enrolled in college.

With the help of federal, state and institutional aid, Murphy, 46, expects to graduate in 1992 with a degree in elementary education from Indiana University Northwest in Gary, Ind. The college financial aid she receives has led to a drop in her Food Stamp benefits (from about $250 to $148 a month), but Murphy has managed to make ends meet, although sometimes just barely.

"After the divorce, I wanted to do something positive for me and my children. I didn't want to work in a factory," Murphy said about her decision to go to college. But she also knows that her commitment is unusual for many in her circumstances, and last summer she started a support group on campus, called the New Majority, to encourage other adult learners "who are a little afraid to come in and stick it out."

Whether they're called the new majority, returning students, or adult learners, this category of college students has been increasing steadily. The U.S. Department of Education says that in 1987, the most recent year for which figures are available, 41 percent of all undergraduates were 25 years and older. The number of undergraduates over age 25 more than doubled between 1972 and 1987, from 2.5 million to 5.2 million students. (According to 1988 Census Bureau figures, the majority of students 25 and older are white, with 10.4 percent black and 5.5 percent Hispanic, about the same as the traditional college-age population.) And a College Board study projects that these students will be in the majority by the year 2000.

Traditionally, most college students enrolled at age 18 right out of high school and attended classes full time. So-called nontraditional students are those who are older or who are attending school part time, or both. Many nontraditional students are enrolled in urban, public institutions and two-year community colleges, mostly because of their relatively low costs, although a few private institutions, such as Northeastern University in Boston, serve substantial numbers of older students.

Even as these adults stream to campus in increasing numbers, many question how well a system designed to serve an 18-year-old supported by his or her parents works for students like Margaret Murphy. And when talking about the issue of access to higher education, financial aid is one of the most important factors.

In a way, Murphy is lucky. She has so little that she had no problem qualifying for aid. And because she doesn't work, she can attend school full time, which makes her eligible for aid that someone taking only one or two courses at a time can't get. Indeed, the system discourages her from working while attending school: If she earned money, her government support would likely be slashed, and at least now her children's health care costs are covered by Medicaid.

In fact, students of any age are eligible for financial aid, but it is the specific circumstances of many adult students that can make it more difficult for them to receive the aid they need. "There are a number of ways people think the system is disadvantageous to older students," noted Arthur Hauptman, a consultant to the American Council on Education. Older students, said Hauptman, have often left a job to return to school. In addition, "they have fixed living costs and often have families to support, and there's a feeling that the traditional needs analysis system doesn't recognize the needs of the family while a husband or wife is going to school."

By comparison, a traditional student from even a needy family can usually count on a place to sleep and food to eat. "An 18-year-old living at home can usually finance education through a part-time job," said Marie Bennett, coordinator of student benefits and support services at Northern Virginia Community College, where the average age of students is almost 30.

At about $85 a course, Northern Virginia Community College can be considered a bargain. Yet, Bennett pointed out, living costs are high in the area, and many adult students "need rent, food and so forth for their families, so even this college can be expensive to finance for a two-year period." In addition, child care can be a big expense for adult students.

Because of their financial obligations, older students usually work. At the University of Massachusetts at Boston, where the average student is more than 27 years old, some 95 percent of freshmen this fall work at least 20 hours a week, and many have full-time jobs, said Corine Williams Byrd, director of student financial management.

Byrd says about 60 percent of the approximately 13,000 students enrolled would be considered nontraditional. Many are separated or divorced women. Some are veterans. Others are simply stuck in dead-end, low-paying jobs.

The catch-22 for adult students who continue to work is that it usually forces them to attend school part time, which can reduce their eligibility for financial aid. In fact, college students enrolled less than half-time are not eligible for the two largest federal sources of aid, Pell Grants and Stafford Loans.

Concerned that the financial aid system favored traditional students, Congress in 1986 changed the law to allow Pell Grants, which provide up to $2,300 per student each year, to go to students enrolled less than half time in college, but this provision has since been put on hold amid concerns about the cost involved and spreading the Pell Grant dollars too thin.

Byrd has lobbied for the change in Pell Grant eligibility. "Our students often can only take one course or maybe two, because they have to work to take care of their families," she said. Bennett, however, acknowledged that, "under current funding levels, it's difficult to justify spreading the money around even more."

And even if they manage to start school with a full course load, older students can be sidetracked easily from their studies. A sick child, a widowed parent, a job transfer can all put an immediate end to the semester for an adult. "It doesn't mean they're less committed, but they might have to leave for the semester," said Peggy Gordon Elliott, chancellor at Indiana University Northwest, where more than half the students are enrolled part time.

Another factor that places older students at a disadvantage is that financial aid is based on income earned the year before applying for aid. Since this information is easily verified with a tax return, it is an accurate way to measure need for a traditional student whose parents will probably earn about the same amount the next year.

But for adult students, who may leave their jobs to enroll in school, or whose economic situation may have changed through divorce, for instance, the use of the prior year income to determine eligibility for aid can be misleading. "For independent students, the concept is inherently flawed," said Lawrence Gold, an education consultant whose book, Campus Roadblock, details the obstacles that nontraditional students face in going to college.

Adults also may lose other government benefits if they go to college. Food Stamps or Aid to Families with Dependent Children are likely to be cut if financial aid is awarded, as happened in Margaret Murphy's case. Also, Gold noted, a displaced worker collecting unemployment often cannot collect benefits if the worker wants to attend, say, a community college to get more marketable skills. Federal law allows unemployed workers to get training while receiving benefits. However, Gold found that because of state regulations and individual caseworker discretion, few unemployed people are able to go to college while collecting benefits.

So how do adults manage to pay for college? Many get financial aid; others work, enroll at low-cost institutions, take advantage of employer tuition benefits and borrow money.

Consider Michele Lee, 42, who earned her B.A. in English and in black and women's studies in 1990 at the University of Massachusetts at Boston, and is now working toward a graduate degree in American studies. She left a bookkeeping job to enroll in college, and borrowed about $20,000 while earning her undergraduate degree. Although she had four children to support, Lee said, "going to school was a lot easier than having no future."

And now that Lee is working in the university's financial aid office, she gets tuition benefits, too. According to a 1989 Department of Labor survey, about 70 percent of workers at mid- and large-sized companies were eligible for tuition benefits to take job-related courses, while 18 percent of workers were eligible for non-job-related tuition benefits.

There are also a small number of private scholarships targeted to nontraditional students. Since 1974, Clairol has been offering grants of up to $1,000 to about 50 women annually who are at least 30 years old and want to go to college to fulfill a career goal. The grants can be used for part-time study, and to pay related expenses such as child care and books, said Ellen Anderson, director of Clairol's public service programs.

One of the biggest blocks of all for adult students is the perception that they're not eligible for financial aid. "Lack of information is the biggest handicap," Gold said. "Adults feel they're not eligible for any aid, college catalogues usually don't let them know what their potential for aid is, and financial aid offices are closed at night."

With this in mind, Byrd sends financial aid forms to every student enrolled at the Boston campus and recommends they apply for aid, but still, she said, "many just don't do it."

Although most colleges and universities are geared to the needs of young adults just out of high school, others are taking steps to improve the environment for older students, realizing not only that adults are providing new blood at a time when the traditional college-age population is declining, but also that they are often serious, goal-oriented students. At Northern Virginia Community College, for instance, the majority of adults are seeking credentials for jobs, Bennett said.

And at the University of Maryland at College Park, women 25 years and older have the highest grade-point averages on campus, said Barbara Goldberg, co-coordinator of the Returning Students Program, which serves the 4,300 undergraduates over age 25 on campus. This group now makes up 14 percent of College Park undergraduates, she said, up from about 10 percent in 1985.

To serve this growing group of students, Goldberg's office provides workshops, courses and newsletters that focus on such areas as financial aid, course and instructor information, time management, study skills, and career exploration. "Adults primarily need information and support," Goldberg said, pointing out that these students generally don't have the networking advantage that younger students get through the residence halls, student unions and other typical campus hang-outs. Not surprisingly, adult students are least interested in the leisure activities offered at college, she continued. "They just don't have the time."

Debbie Goldberg writes frequently about education.