In the heady days of school construction, as enrollment in Prince George's County classrooms climbed toward its all-time peak of 163,000 in 1971, schools sprang up on vacant lots in residential neighborhoods across the county. Now the root of a thorny county problem is that some of the schools are in the wrong place.

With the student population down to 116,000 and expected to fall to 100,105 by 1985, the Board of Education has closed 54 schools and plans to shut 11 more. Seven closed schools will be kept by the school system for other uses, such as special education facilties and a vocational center. Seven already have been sold, and others are being used by the county government for office space. But 30 schools are standing empty.

"When you have a big school building sitting there and not being used, what do you do with it?" asks Ruth Senes, legislative liaison for the Maryland-National Capital Park and Planning Commission in the county. "Most of the time it's sitting right smack in the middle of a residential area--and you can't convert it to a single-family home."

The school system is under a temporary court order to retain 20 empty schools, pending the outcome of a segregation lawsuit by the NAACP against the school system. But school and county officials are only too aware that they have millions of dollars worth of idle real estate to dispose of.

Schools no longer needed are handed over to the county government. In an effort to get rid of the schools as soon as possible and to avoid the problems of residential zoning, county officals have proposed legislation, drafted by Senes, that would grant a blanket zoning exception to unused school buildings. Under this proposal, the County Council would not have to adhere to existing zoning, but could judge each proposed use individually.

County administrative officer Kenneth V. Duncan, who has been circulating copies of the proposed bill to county municipalities for their opinions, says the bill would allow potential buyers to sidestep the sluggish rezoning process, and open empty schools to a wider range of uses.

A good elementary school can fetch about $500,000 for the county, and the sooner it's sold, the sooner it's back on the county tax rolls, he said, adding that maintaining an empty school costs more than $20,000 a year.

Susan Steele, who has studied the empty-school problem for the county planning department, said residents of municipalities where schools are located have little to fear. Each proposed use would be examined individually by the planning department and the County Council, which would hold a public hearing. The proposed legislation would require the council to determine that the proposed use was "compatible" with its surroundings and not a "nuisance." If the building is within a municipality that objects to the proposal, a two-thirds vote in the council would be needed to approve it.

Under normal rezoning procedures, Steele said, the use would be studied by the planning department, a zoning hearing examiner, the planning board and, because county property is involved, the County Council.

Property given a "commercial" zoning to allow a quiet research organization to use a school building could become the site of a fast-food outlet under usual zoning rules. But the proposed bill would require that each use of the property, and any subsequent changes, be examined individually by the County Council.

Most important, Senes said, the proposed bill would allow developers to use their imaginations in finding uses for old school buildings, and the council to "put developers' ideas to a test of compatability."

But leaders of many county municipalities, who watched the state General Assembly this year defeat several bills that would have given them more control over school buildings in their jurisdictions, have greeted the proposed legislation with suspicion. They are worried by the proposal's lack of requirements for a zoning examiner's hearing and specific density or height restrictions, and by the fact that no use would be explicitly forbidden.

College Park administrator Leon Shore says the City Council "opposed the concept" because it wants "more protection than special exceptions would provide." The city would rather "preserve the integrity of a residential neighborhood than permit an objectionable use in order to sell," he added.

Cheverly administrator Joseph Jones said his municipality "agrees with College Park. We did not favor this bill. We felt that adequate zoning procedures exist to cover this." The regular zoning process, he said, provides "adequate channels" and should apply to unused schools.

Greenbelt's mayor and City Council voted their opposition to the proposed bill two weeks ago. City Clerk Gudrun Mills said the proposed special exceptions would circumvent existing zoning procedures and reduce the city's ability to protect residential neighborhoods. Meanwhile, the City Council has requested a meeting with county officials in an effort to gain control of the abandoned North End Elementary School.

Hyattsville hasn't made a final decision, but Mayor Tom Bass said he and some council members questioned "whether they should get rid of the schools at all." Bass said school buildings should be kept by the county for public use, and re-use as schools if needed in the future.

"We know it's a very sensitive thing," said Phil Schwartz, the county property manager in charge of disposing of the unused schools. The municipalities "think of it as their school," he said. "At the same time you have to look at the broader view, and understand we can't always turn a school over to them for recreation. Somebody has to pay operating and maintenance costs of a school, and these are a miniumum of $75,000 to $80,000 a year. And a lot of communities can't afford it. Neither can the county, quite frankly."

Duncan complained that, despite vigorous marketing, the fact that potential buyers must wait 18 to 24 months for rezoning decisions "is a big disincentive" and drives property buyers elsewhere. And the number of community groups, churches, and private schools that want the buildings, and could afford to buy them, is dwindling, he said.

Whatever the result, all agree that the schools cannot sit empty, even though most of them are in residential neighborhoods. The former Holly Park Elementary School in Seat Pleasant, which is only partially used by the Board of Education, attracts teen-age drinkers and its parking lot is littered with broken bottles, Steele notes.

And G. Gharles Moore, city administrator for Bowie, where three empty schools have been targets of vandalism, said the problem is "serious. We're anxious to see action taken on them so they don't remain that way."