More than 1,400 Prince George's County students take their seats in a dozen new magnet schools today, but the county Board of Education is still scrambling for funds to support the ambitious experiment in desegregation.

The 1985-86 school year opens with school officials optimistic that the magnet schools and an additional 10 "compensatory" education programs will resolve the county's 13-year-old desegregation lawsuit.

But over the official enthusiasm hangs a lingering cloud -- the question of how the $8.9 million program will be funded and the threat of legal action by the county NAACP, which wants a commitment that the money will be there.

"The money is supposed to be in place," said Thomas A. Newman Jr., a member of the NAACP and plaintiff in the suit. Newman said promises of financial support from politicians were not enough. "I want something more concrete," he said, "and so does Judge Frank A. Kaufman," the federal judge overseeing the suit.

The new programs, approved by Kaufman for a one-year trial, are the most radical of the solutions attempted in years of trying to better integrate the county schools, which are more than 57 percent black.

The magnet schools offer either special programs for talented and gifted students or before- and after-school day care, designed primarily to attract white students into predominantly black neighborhoods. The compensatory education programs have increased funding in 10 predominantly black schools that officials contend cannot be desegregated because of their location.

Administrators already have spent nearly $3 million on computers, laboratory equipment and new teachers, with the assumption that county and state coffers will reimburse what is being borrowed from elsewhere in the school budget. While state legislators and county officials express support for the program, they have so far made no hard commitments about funding.

"We are heavily invested," said school spokesman Brian J. Porter. "The situation has not yet come to a critical head. But unless we receive full assurances and visible efforts are made to secure funding, people are going to become very jittery."

Superintendent John A. Murphy said yesterday he was reassured after a meeting Saturday with County Executive Parris Glendening and Gov. Harry Hughes. "We're taking everyone at their word and fully expect to be reimbursed for the money we're spending," he said.

The costs may be reduced this year by a $4 million federal grant the county is seeking and revenue from the day-care programs. But there is also the question of who in future years will pay for the programs, expected to cost at least $12 million annually as new magnet schools are added.

In a recent letter to school board attorney Paul M. Nussbaum, an attorney for the county NAACP said the civil rights organization wanted more concrete information on the status of funding for compensatory programs and would take the matter to the federal judge overseeing the desegregation lawsuit if necessary.

"Since June, we have expected the school board to pursue as vigorously as they could outside sources of funding," for the desegregation programs, said George H. Mernick, another attorney for the NAACP. He said the organization had yet to decide whether to push the board to file suit against the state or county to secure the money.

In a June agreement with the NAACP, the board agreed to take "appropriate legal action" against the state or county if necessary to receive funding.

Glendening said the funds most likely would come from a combination of state and local sources, but he is seeking approval by the General Assembly of a funding formula that will guarantee ongoing support.

"The program is going to be funded," he said. "The worst that is going to happen is that we'll have to pull the belt in another notch."