SECRETARY OF EDUCATION William J. Bennett may have touched nostalgic chords in old collegians last February when he described college students as sun-worshipping, car-driving stereo buffs, but the picture he conjured up no longer describes the reality in today's colleges and universities.

Despite the images of thrills in Fort Lauderdale paid for with Daddy's charge card, a new kind of student is emerging: only 57 percent of today's college enrollment comes from the 18-to-24-year-old age group, down from 68 percent in l963-64, and the figure is declining towards a minority. A college student is nearly as apt to be a working man or woman seeking a two-year certificate, a baccalaureate that was missed earlier in life, or an advanced degree that might enhance earning power or meet career requirements.

This change may suit college administrators fine -- it keeps their enrollments high -- but we are now seeing younger, poorer seekers of higher education competing with older, richer ones for long-term, low-interest federal loans as the newcomers take advantage of a program that was not created for their benefit or for persons of middle-to- high income.

"Increasing numbers of student- aid recipients at public colleges and universities are white, older than traditional students, self-supporting, and attending college part-time," according to a report released recently by the American Association of State Colleges and Universities.

Ample data exists showing that college enrollment among minorities and poor whites is dropping.

Another report by the association states, "More middle-income students are eligible for aid now than was the case in the mid-1970s . . . . Low-income students have suffered while middle-income students have benefited."

None of these facts was reflected in the brouhaha over Bennett's attempt at humor while advancing the administration's efforts to curtail student aid. Academic protestors, fearful of cuts in ever-increasing federal funding, found it more profitable to attack the sentiment than the accuracy of the stereotype.

The changing demographics of college students are particularly relevant now just as the debate about cuts in federal assistance for higher education heats up. After increasing 378 percent per student (adjusted for inflation) from 1963-64 to 1980-81, student aid from the federal government has decreased 23 percent between 1980-81 and 1983-84. The cost of getting a college education, on the other hand, has increased more in the last three years than it did in the entire period from 1963-64 to 1980-83. Between 1963-64 and 1982-83, real expenses for students -- that is, the expenses over and above inflation -- rose 23 percent at private, four-year colleges, 19 percent at community colleges, and 13 percent at public, four-year colleges.

We have come to associate quality with expensive. With Harvard and Yale and other Ivy League schools now at $15,000 a year and certainly not wanting for more applicants than they can possibly accept, a kind of trickle-down effect brought others up, too. Georgetown University, for example, costs nearly $8,000 in tuition and basic fees alone, American University about $7,000, George Washington University more than $6,000, Howard University $3,000, the University of Maryland $2,000, and George Mason University about $1,400 for in-state students.

With little questioning of why these costs have increased so radically, the federal government has set out to pump larger and larger amounts of money into academia to pay for them.

Financial aid to students from all sources -- primarily grants and loans -- jumped from $500 million in 1963-64 to $18 billion in 1981- 82. That is five times as fast as college expenditures. The federal government's contribution to student aid jumped from 40 percent of total aid (including scholarships and other outside sources) in the early '60s to 80 percent in the early '80s. Private aid grew during this period, but the federal contribution grew much faster, thus increasing the federal share of the subsidy.

Eligibility for aid has increased as well.

The Middle Income Assistance Act, passed by Congress in 1978, expanded "post-secondary" aid eligibility to encompass not just full-time college students, but also non-degree-seeking students, vocational/proprietary school students, students studying part-time, and even non-high-school graduates who are deemed to have "ability to benefit from the training offered."

This act eliminated any need-base for getting a government guaranteed student loan. Almost anybody could get one. In 1981, Congress passed the Omnibus Reconciliation Act which re-established some criteria for getting loans. However, even for those students who have an adjusted gross income above $30,000, they still can get a loan if they pass a needs test -- which isn't hard to pass if you are clever enough.

Between and 1979 and 1984, the number of federal student aid recipients increased 24 percent, and the federal loan program recipients more than doubled. Total federal aid given or loaned to students increased from $7.1 billion in 1979 to $12.2 billion in 1984 -- a 72 percent increase in aid that outstripped the increase in college costs.

Stories abound of abuses of student aid. Whether or not they reflect the experience of the bulk of college students, they have come to nag at educators and aid-givers as stories of coffee makers costing thousands beleaguer the Defense Department.

One is about the students who put their loan money in banks at current high interest rates and then pay it back after graduation at low government rates. Another is of some 7,000 to 13,000 students getting loans although their families report anuual incomes in excess of $100,000, which would run counter to the spirit, but not the letter, of the law.

And the rate of repayment is not good. According to the Department of Education, 10.7 percent of its student loans have not been paid back when due. That leaves the department holding the bag on $5.1 billion in overdue loans.

The big raise in both aid and expenses beyond the rate of inflation has never been satisfactorily explained, although colleges give many reasons, such as the need to catch up with the ravages of inflation, the need to modernize, and the need to pay more for faculty members who might be lured to higher salaries elsewhere, though where that lucrative "elsewhere" is is rarely defined.

Colleges and universities may argue that they have had to raise their prices to make up for years of neglect, but this argument fails to convince educational experts. Dr. Ernest L. Boyer, former U.S. Commissioner of Education in the Carter administration said last spring, "Pricing is really reaching the outer limits with no rational basis."

Bennett, speaking before the U.S. Chamber of Commerce in April, addressed the increasing cost of higher education: "What are we supposed to do?" Bennett asked, "pay the entire bill no matter what the cost? Isn't it queer that the more money the federal government puts into the system . . . for loans, grants and even the tuition, that the (effect) ultimately has got to be to drive those costs up? How come we never talked about cost control at colleges and universities? We talk about hospital cost control. Why can't we talk about university cost control?"

The suspicion is strong that, as with just about everything else during an inflationary period, the colleges' impulse was to charge whatever the market would bear. And the market has changed to older, often working people who are not only eligible for federal loans along with younger, poorer students, but are apt to have more earning power.

College enrollees over 25 years of age more than doubled in number between 1970 and today (up 122 percent), while those under 25 increased only 12 percent for the period. Part-time enrollees now account for almost half -- 44 percent -- of the total number of students at American institutions of higher learning, compared with a third in 1970.

The old college-student stereotype falls apart even more when we look at where today's new breed of college students go to school. Enrollments at two-year colleges have jumped 116 percent since 1970, while four-year institutions showed only a 17-percent gain for the period. Enrollees in two-year institutions now account for 40 percent of college enrollment compared with 26 percent in 1970. The shift is helped by two-year colleges being cheaper and generally not imposing rigorous entry and exit requirements.

When it comes to abuses, the colleges themselves are unlikely to seek reform, or even sit still for any changes at all in student aid. As participants in a growth industry, they would seem to prefer to go with the flow -- particularly the two-year colleges. They account for 40 percent of the total college enrollments today and show the greatest growth -- some 58 percent of all colleges founded in the past 10 years were of the two-year variety -- and hence exhibit the greatest awareness of market trends.

This proliferation of two-year colleges, with the biggest enrollment gains among the public ones, will put even more pressure on the federal government's student grant and loan programs. Public two-year colleges, which get 80 percent of their total student aid from the Department of Education, are least able to provide loans and scholarships of their own. It is they, not the four-year schools, that appeal so strongly to the over-25 part-time students now filing into classrooms. And, as the federal system works, these students or any student attending college at least half-time can apply for aid, despite the fact that the federal student-aid program was not designed to enhance the careers or enrich the lives of adults earning comfortable salaries.

There is no question colleges and universities are in trouble. They face the realities of a declining population of typical college-age students, threats to the federal support they've relied heavily upon, a period in which the greatest job demands are in skill areas that do not require a college education and the public's disenchantment with the quality of higher education.

To survive they are going to have to bring costs in line with quality of the product. A Study Group on the Conditions of Excellence in American Higher Education, in a recent report, stated, "Virtually all institutions of higher education, public and private, are dependent on some form of enrollment-driven funding and hence tend to serve the changing whims of demand rather than student needs." There is abundant evidence that a college education pays off and that a good education pays off more than a poor one.

And, of course, Uncle Sam needs to get his house in order, too, and come up with some answers about where its student aid money has been going and to whom and for what kinds of higher education. The Department of Education cannot say today who's been getting its money to go to college by age of student, family-income level, whether the student is full-time or part-time, going to a two-year or four-year college. About all we know for sure is that about half of the 7.5 million full- time equivalent students get at least part of their college education paid for by the taxpayers.

Until the federal government comes up with some hard figures showing how it is spending its ever increasing dollars for assistance to students going to college and the institutions of higher education account for their soaring costs, cries for more student aid dollars don't make a lot of sense.