The Prince George's County school superintendent yesterday proposed closing 43 schools over the next three years as an ecomony measure. The closing program -- the most extensive in the Washington area -- calls for eliminating a fifth of the county's elementary schools.

Superintendent Edward J. Feeney proposed to the school board closing 31 elementary schools and 12 junior highs by 1983 (a 13th would be closed in 1985); 15 of the elementaries would be closed next year.

The program, in which students would be shifted from underenrolled schools, would save the school system $35.2 million and represents the first attempt to analyze schools on a countrywide basis and project enrollment patterns through the current decade.

In recent years, school closings necessitated by falling enrollment have proved controversial in the Washington suburbs, with parents of the affected students frequently mounting vehement opposition to plans to close their neighborhood schools.

The Prince George's plan has been anticipated since October when school officials reported a continued sharp decline in enrollment, from 127,000 students last year to 122,000 this; public school enrollment peaked in the county at 163,000 in 1971-72. Enrollment is expected to fall to 100,000 by 1985.

The economic pressure to close schools is particularly acute in Prince George's because voters there approved a county charter amendment that limits revenues from the real estate tax to the amount collected in fiscal 1979.

According to school administrator Ed Felegy, great pains were taken to insure that the effect of the closings would be evenly distributed throughout the county and based on the most rational way to utilize plant and equipment. The planning also took into account the county's seven-year-old busing plan for racial desegregation. Felegy said there would be no substantial alteration in the schools' racial balance as a result of the consolidation and closing plan.

School officials stressed the urgency of the need to shrink the size of the system, a week after Feeney submitted a proposed $294 million budget that he said was tailored to deal with what he called a "crisis" and ensure the continuation of quality education in the county.

"If we do nothing at the elementary level between now and 1983, we would have 52 schools with less than 300 students," said Felegy, saying that a desirable elementary school program requires an average of 400 students.

Felegy remarked that, "what we see happening in Prince George's parallels what we see happening nationwide." He noted that over the past decade Baltimore County has lost 23 percent of its school population and Montgomery County 19.8 percent.

The closing proposal incorporates a plan approved last year to convert 25 of the system's 40 junior high schools to two-year "middle schools" for seventh and eighth grades. Three junior high schools would be closed next year. Of the 12 that would be shut by 1983, two would be incorporated into plans to combine elementary schools into the junior high school buildings and two would be used for extensions to existing high schools.

Since 1977, Prince George's has closed 20 elementary schools and one junior high, saving an estimated $8.8 million to date. Eighteen of the elementary schools scheduled for closing in the new plan are north of Central Avenue, which bisects the county from east to west, and 13 are below. Nine of the schools are inside the Capital Beltway and 18 are beyond that highway, which often marks the border between black and white Prince George's County.

School spokesman Brian Porter noted that four of the schools to be closed were built before World War II and 17 before 1960. Six of the schools slated for closing would need roof replacements within five years, nine would require electrical re-wiring, and 23 have county building code violations that would have required renovation expenditures not included in the projected $35 million savings.

No action was taken on the inch-thick plan at the meeting last night. School officials will ask the board for permission to hold a series of informational meetings in the affected communities at the next board meeting on Jan 8.