With little more than a month before schools open for the fall semester, Einstein High School social studies teacher Guy Williams still doesn't know whether he has a job in September.

Williams was one of more than 900 teachers declared "surplus" last spring by the Montgomery County school system. "If I stick my neck out and wait until the end of August, I might end up without a job," he said. "If I want to be sure I have work in the fall, I have to apply somewhere else now. It's pretty bad for morale."

Within the last three years, in the Washington area have closed more than 30 schools and school officials are predicting that dozens more will be shut down during the next decade.

Both the closings and the threatened teacher layoffs are reflective of the single dominant influence in education today: an unprecedented decline enrollments.

After nearly three decades of record growth, the declining enrollments in the Washington area and across the nation carry grave implications, educators say, including massive school closings, teacher layoffs, and likelihood of serious morale problems among teachers and administrators and the necessity of substantial curriculum revision.

In Washington, Maryland and Virginia, officials are projecting enrollment drops totaling more than 400,000 students between the beginning of the 1970s and the mid-1980s.

Nationally, between now and the fall of 1983, school enrollments will fall from 49.3 million to 44.4 million, according to the U.S. Office of Education, a 10 per cent drop in six years.

Never before in the nation's history have school enrollments fallen so drastically, although enrollments did decrease between 1941 and 1945 as a reduced depression era birth rate made its impact on the schools.

But the current decline - the result of an unequaled drop in the national birth rate - exceeds all previous decreases, both in magnitude and in duration. By 1990, officials say, enrollment in public schools and in colleges, will still be below what it was during the peak years of the 1970s.

There is some evidence that the early months of 1977 may have marked a turnabout in birth trends and that birth rates may once again increase. But it is too early, officials say, to tell whether the turnabout will be permanent or to gauge its impact.

In the Washington area, the declining enrollments are already affecting teachers. "There is a substantial lack of job opportunity and job mobility," says Lee Vosper, president of the Arlington Education Association. "The morale has been bad in Arlington. We've had RIFs (reductions in force) for the last five years. This has been very demoralizing to the troops."

Enrollment in Arlington's schools peaked in 1964 - about six years earlier than other area jurisdictions - at 26,927. For September, there is a projected enrollment of 18,420 with additional declines forecast into the 1980s.

TO deal with the decreasing student populations, Arlington has already shut down two elementary schools and closed half of another. At the end of the next academic year, it plans to close two junior high schools and revamp the secondary school curriculum to shift the ninth graders to the county's three senior high schools while assigning seventh and eighth graders to intermediate schools.

To protect itself from a possible teacher excess, Arlington sent RIF notices to 106 teachers this spring. In past years, attrition has enabled the school system to rehire all but a few of the teachers receiving such notice, often at another school or in another job. But this year, officials say they expect as many as 60 or 70 may find themselves permanently dismissed.

Even for those do get rehired. "It's very demoralizing," said a Montgomery County economics teacher, who received RIF notices each of the last two springs, only to be rehired during the summer.

"It comes in the spring after you've put in a lot of work for the year. You try to establish a base in the school, put in some overtime and do all the things that go into making teaching successful and you get a formal notice saying they're sorry but they can't promise you a job in the fall."

Montgomery County, which last year began an extensive program of school closings, sent out 992 RIF notices this spring, 750 a year ago. Most were rehired.

In the same timespan, it shut down six elementary schools and a junior high school effective September 1976 and nine more elementary schools will close with the start of the 1977-78 school year.

For the future, as many as 30 more school closings are planned, including up to 9 secondary schools, as enrollments are expected to plummet from 1972's peak of 126,311 to 3,804 in September, 1982.

Here and elsewhere such closings are painful and controversial and are often accomplished over the objections of parents and students. In Evanston, Ill., last spring a group of homeowners even went to court in an unsuccessful effort to keep their neighborhood grammar school from closing.

"When parents block school closings, they are not fighting to save a building but to preserve a unique personal investment," said Katherine E. Eisenberger, director of special projects for the Ithaca, N.Y. schools, in an article in School Management magazine.

"The staunchest school supporter and the greatest educational advocate is the parent . . . When parents view local school closings, what they see is the threat of losing their investment and having to begin all over again . . ."

While Montgomery County has taken the lead so far in terms of school closings, the issue is acute in all Washington area school systems with the possible exception of Falls Church, the area's smallest - although declining enrollments are of concern there too.

In Alexandria, declining enrollments made it possible to close one school, Cora Kelly, which was located in a flood plain, but there are no firm plans for additional school closings.

Prince George's County will close 10 schools effective this September and schools officials project more closings, although exactly how many is unclear.

Prince George's County enrollments 1980, according to projections, then will bottom out at 130,000 students in begin to climb again, but those figures are far more optimistic than estimates by the state.

In Washington, School Supt. Vincent Reed has urged that 36 schools be considered for closing in the face of declining enrollments combined with a surplus of new schools, but the School Board has not acted. The city's school enrollment has plunged from 149,000 in 1969 to the current 126,587 and it is projected to drop even further to 109,400 in the fall of 1980.

Of the major school systems in the area, Fairfax County faces the smallest enrollment decreases, but because of uneven growth patterns, the county is in the position of building new schools in some areas while closing schools in others.

From a high of 136,894 in 1975, Fairfax schools have fallen to a projected enrollment of 132,579 when schools open in the fall and forecasts are for enrollments to drop to 125.357 in 1981 before they begin to go back up again.

But however traumatic it may be to a neighborhood or community, the closing of a school is only one of several implications of the declining enrollments.

In addition to morale problems caused by RIFs and teacher layoffs and equally serious problem occurs when declining enrollments bring about a situation where staff promotions are few and far between.

"Where the possibilities for promotion are very small, how do you keep people productive and happy?" asked Martin Katzman of Harvard's Department of City and Regional Planning at a seminar in Washington.

While only Montgomery and Arlington schools have sent out RIF notices in significant numbers, other systems have cut back sharply on hiring. The result is a progressively older and a dwindling percentage of young teachers on the staff.

Nationally, according to estimates of the National Education Association, only 94,050 of the 185,750 graduates of the nation's teachers colleges who sought teaching jobs last year found them. This left a surplus of 91,700 teachers and the teacher glut is expected to grow each year.

In addition, decreasing student populations, warned the National Association of Secondary School Principals in recent bulletin, are likely to be accompanied by pressures to reduce a curriculum that is rich in electives to one that is little more than the "bare bones" essentials.

While forecasts suggest that by the mid 1980s the enrollment declines will have bottomed out, projections are that the subsequent increases will not be enough to offset decreases.

State projections in Maryland have school enrollments falling to a low of 725,211 in 1986, down from a 1971 high of 922,051. Last year Maryland schools had 856,799 students.

In Virginia, officials predict an enrollment low of 948,000 in 1986, down from the peak of $1,143,000 in 1975. Last year, Virginia schools had 1,141,000 students. The District of Columbia schools do not have projections beyond 1980.