Controversial school closings in Montgomery and Prince George's counties designed to save money may instead cost local taxpayers millionsof-dollars more, Maryland officials said yesterday.

Although school officials have said they save up to $100,000 for every underenrolled school that is shut down, it now appears that the county governments may have to pay far more than that amount when they dispose of the vacated school buildings. In many cases, the counties may lose money on schools that are closed, officials said.

The problem results from the state's interpretation of laws that provide for financing school construction with state funds. The state Interagency Committee for School Construction has decided that these laws, which were passed in an effort to equalize the burden of public education among taxpayers in the state, do not apply to schools that have been closed and put to different uses.

The state has told Montgomery County that it will have to pay about $2.8 million for construction debts still owed on the 18 schools it has closed since 1976 and turned over to the county government. Prince George's will have to pay at least $900,000 for five schools that its school board has closed, and probably $1.3 million more for five other closed schools that the county is already using.

Both counties can avoid losing money on past and future school closings only by selling the school buildings at good prices or by leasing them to nongovernment groups at rates that will pay off old construction costs, local school officials said.

In many places, however, school buildings are hard to lease or sell because they are in residential areas where businesses or other possible investors cannot move in. For some schools, the counties would have to raise as much as $500,000 to pay off construction debts without losing money.

"There's got to be some entrepreneurship," conceded Eliot Robertson, who heads the Prince George's County budget office. "It will largely be up to the imagination of the county managers, once we turn surplus buildings over to them."

School closings in recent years have been caused by falling enrollments, but most closings in both counties have been controversial. Community groups have long contested the estimates of school officials about how much the closing of a school actually saves. Those arguments have recurred this month as the Prince George's School Board considers 20 schools for possible closing June 30.

The counties have disputed the authority of the interagency committee, which is composed of the state school superintendent, state secretary of general services and state secretary of planning, to force them to make up the debts on closed schools.

State government sources said yesterday that a state attorney general's opinion on the issue now under final review will uphold the authority of the state committee to approve the use of school buildings for other purposes, and to set conditions for such transfers -- including local responsibility for debts.

"Our concern is that once a school building is no longer used for education, it could be turned over to a private party by the county government," said Leo Ritter, executive director of the committee's staff. "It could be leased to a private school, or sold outright. Meanwhile, the state would still be paying for it.

"It's a problem where the taxpayers all over the state of Maryland would be paying debt service on buildings that were not used for education. If the use of these buildings has changed, the taxpayers have the right to change the conditions of payment on them."

Since 1976, Montgomery County has taken over 18 schools from the school board and is using them as administrative offices and for special programs for the elderly and handicapped. The county has also leased many of these schools to private schools and programs, school officials said.

Five Prince George's schools -- including three elementary schools that were closed by the board in 1977 because of underenrollment -- have been declared surplus and have been transferred to the county, pending the approval of the state committee Robertson said that some of the buildings have been targeted for possible use by the county as police stations or as privately operated senior citizens homes.

In addition, Prince George's school officials have already transferred five other closed elementary schools with outstanding construction debts to the county government. In some cases, school officials have temporarily evaded committee orders to pay the debts by granting the county permits to use the building rather than transferring ownership. The counties do not have to directly approach the committee about the use of a building unless a transfer of ownership is involved.

"Of course, we evaded the committee, said Robertson. "Where's the use in leaving a building vacant while this debate is going on?"

Montgomery school officials have also managed to keep school buildings in use by granting long-term leases of school buildings to the county at minimal charges. Neither arrangement will be allowed to continue if the attorney general's opinion favors the committee, Ritter said yesterday.

"Once we have a ruling, we are just going to have to sit down with the counties and work out an arrangement for the payment of the outstanding debts on these buildings," Ritter said. "The board may not force the counties to pay all of it, but I don't know -- it will have to worked out."