The Montgomery County school board's attempt to make ambassadors and other foreign diplomatic personnel pay tuition for their children who attend county schools was overturned yesterday by the Maryland Board of Education.

In a unanimous decision, the state board concluded that "the constitutional and statutory requirements of free public school education require the provision of a free education to all bona fide residents of the state . . . and does not permit the charge of tuition to individuals who are in fact residents of the State."

The Montgomery board's tuition policy, strongly opposed by both the foreign diplomatic corps and the U.S. State Department, would have affected about 2,000 students whose parents are exempted by international agreements from paying some of the local taxes used to support public schools.

The board decided last October to adopt the policy -- and reaffirmed that decision Aug. 20 -- because of the approximately $1.3 million in additional revenues the tuition charges would bring in.

The policy was pushed for by some Montgomery residents, in particular the Montgomery County Taxpayers' League, which charged that the diplomats were getting a "free ride."

But it was immediately challenged in court by six employes of international organizations.

Alfred Scanlan, the attorney who filed the suit for the six, said yesterday he was pleased with the resolution of the issue by the state board and will drop the suit.

Scanlan had requested a hearing before the state board as the final appeals procedure before the issue went to trial. The state board can hear appeals of any local board decisions.

At yesterday's meeting, he told the state board members the decision to begin charging tuition this September was "a mean and petty policy aimed specifically at aliens.

"If this policy stands, why don't we charge aliens for parks? Why don't we charge them for police protection? It would make as much sense."

Montgomery school board President Marian Greenblatt said she was "very disappointed" with the state board's decision and expected a decision on whether to contest it in court to be made at the closed session today.

"The policy was to assure fair treatment of county residents; to make sure that everyone paid his or her fair share. I don't think Montgomery County can take on the burden of the nation" by providing education for diplomats' children but getting no tax dollars in return.

In a letter this month to Maryland Attorney General Stephen H. Sachs, a State Department legal adviser said that the tuition policy could be construed as an attempt to tax persons to whom the federal government has already given tax exempt status and could produce repercussions for American personnel abroad.

The tuition plan, according to the letter, "places the federal government in the position of violating its international obligations and places the county in the position of usurping the federal role of conducting foreign relations and upholding commitments to foreign governments."

The tuition plan would have resulted in a charge of $1,628 for kindergarten students, $2,403 for elementary students and $2,703 for secondary school students whose parents pay neither property nor state income taxes. It would have provided for prorated bills to parents who pay some but not all of the taxes that support their children's education.