The Prince George's County school board voted unanimously last week to cast its lot with Maryland's richer counties in an effort to preserve the right to spend as much as it wants on educating its students.

The board decided to file a "friend of the court" brief in an effort to overturn a ruling that each school district in the state must spend essentially the same amount on its pupils.

School board attorney Paul Nussbaum cautioned before the vote: "I hope that, if the board elects to go into this case, it is reasonably certain that the future is more aligned to richer families than to Somerset and the poorer families."

Speaking before the meeting, A. James Golato, who introduced the motion, said his "optimistic attitude" convinced him Prince George's must get involved in the case. "Our tax base is going to increase," he said. "Four or five years from now, this county will have the funds to improve and enrich public education."

Baltimore Supreme Bench Judge David Ross ruled in May that the current method of paying for public education, by which some counties spend more of their own money than others, was unconstitutional. Somerset County and several of the state's poorer school districts had sued the state schools superintendent, saying current school financing methods discriminated against poorer counties. An appeal on Ross's ruling is likely to be heard at the end of this year.

If the Ross ruling stands, the state legislature will have to devise a system that ensures equal spending in each county. Although they have little idea how such a system would work, school officials in Prince George's are worried it will force them to spend less.

Golato said it will mean Prince George's students will lose future benefits. "It's like weighing down the best dancer in the chorus so she will not be any better than the worst," he said.

Just as important, he said, would be the loss of local control over public schools. If the state becomes sole master of education funds "local boards of education will have no authority at all. I say it's a monstrosity."

"I'm not sure local control is a key issue right now," said Susan A. Bieniasz, a member of the school board's legislative committee. "But I think it could very dangerously become one."

The outcome of the Ross decision may take years to determine, she said, but it is wise for the board to get involved now. "I really believe it's important," she said. "I don't think we need to become a defendant, but we are enlisting local support and showing a willingness to look at that issue."

Prince George's school officials have been unable to calculate precisely what the school system stands to lose. The county spends more on each pupil than the average Maryland county -- $2,345 in 1979, compared with a statewide average of $2,271 -- and could be forced to spend less if it is told not to exceed the average.

On the other hand, this money was coming from tax revenues which, when divided by the number of students, amounted to less than the Maryland average: Prince George's collected $59,386 for each student in 1979, while the average was $65,286. "There are two measures that are involved," assistant superintendent Elliot Robertson said. "I don't know how it can be evaluated."

Montgomery County, which spends more of its own money on education than any other and saw itself with the most to lose, came to the state's aid as a codefendant. So far, it has spent more than $1 million to pay legal fees.

School officials from Montgomery County and from Howard County, which has already resolved to file a friend-of-the-court brief, said they were happy that Prince George's is on their side.

"I'm pleased that a county such as Prince George's has indicated its willingness to fight this," said Howard County Public Schools Superintendent M. Thomas Goedeke. "If there are a number of counties which have a similar concern, it's anticipated they could have a major effect, and could change the thinking at the Court of Appeals level."

Montgomery County schools spokesman Kenneth K. Muir said, "Because Prince George's is a large school system, we're pleased that they're included." If a good cross-section of Maryland counties joined in, he said, it might make a strong impression on the court.