Boston School Superintendent Robert R. (Bud) Spillane was named superintendent of Fairfax County schools yesterday and said he intends to make the county schools a national showcase for public education.

Spillane, who is credited with raising academic standards and improving discipline and morale in the racially troubled Boston school system over the last 3 1/2 years, told a news conference at Fairfax school headquarters:

"I think there is a very excellent basic program in Fairfax, which is why Fairfax is so important -- because it can become a basis for national leadership in public education."

He cited parental support for the schools and a willingness to pay for education in the county as the foundation for improvement.

Spillane will take over July 1 and will be paid $90,000 a year, a total that school officials said includes a $10,000 yearly payment to compensate him for pension benefits he will lose by leaving Boston.

In addition, he will get about $20,000 worth of yearly benefits described as standard in the Fairfax school system, including health and life insurance, plus the use of a car for business.

The salary and benefits are comparable to those of District of Columbia School Superintendent Floretta McKenzie and Montgomery County Superintendent Wilmer Cody at the top of the compensation paid to Washington area school chiefs. In Boston Spillane was paid $70,000 a year and had the use of a car.

The salary of a new Fairfax superintendent was an issue closely watched by officials in that county and elsewhere in the Washington area.

William J. Burkholder, the current superintendent, decided last year to retire amid a controversy over a $157,000 pay package that the School Board offered him.

The Fairfax school system, with 124,000 students and a proposed budget of $531 million for next year, is the largest in the Washington area and 10th largest in the nation. Boston's schools have an enrollment of 57,100 and a budget of $300 million.

Spillane, picked from a field of 65 candidates, was the unanimous choice of the School Board in a post-midnight executive (closed) session yesterday that ended an aggressive five-month search to find a replacement for Burkholder. He was offered the job in a 12:30 a.m. telephone call that woke him up, and he accepted immediately, he said.

The afternoon press conference was marked by expressions of high expectation. "When we started this search," said a beaming Mary B. Collier, School Board chairman, "we said we wanted a superintendent who could walk on water. We found a superintendent who can work miracles."

Spillane, 51, said he hasn't yet established priorities for the Fairfax schools. But in response to questions, he said he hopes to involve businesses in the school system, is committed to the system's program of improving minority achievement and will address the problem of teacher shortages caused by low salaries.

"It's one thing to say you're committed to higher salaries," he said, "it's another thing to do something about it."

Officials in Boston were generous with praise for Spillane, who took over the schools there in August 1981 after a half-decade of turmoil over court-ordered busing to achieve desegregation.

"I think there is generally a feeling of disappointment that we are losing what I consider to be a very dynamic and effective leader for the Boston public schools," said John Nucci, president of the Boston School Committee, the equivalent of a school board.

"The schools in Boston have improved remarkably, almost miraculously, since Bud Spillane came here," said John Silber, president of Boston University, who is chairman of a committee of Boston-area university presidents set up to advise the Boston public schools.

Colleagues and officials spoke of Spillane as a fine administrator with a firm but low-key and accessible style. They said he took over a Boston system with no financial reporting systems, no budget systems, no promotional standards for students and no standardized curriculum goals, and will leave with all those things in place.

The Boston schools, with a 70 percent minority enrollment, experienced racial strife during the long desegregation struggle. Fairfax County's schools have a student body with a 19 percent minority enrollment.

Spillane said in answer to questions at the press conference that he is looking forward to fresh challenges that the "stable" Fairfax system will provide. "You want me to be honest? No, I won't miss the politics" of the Boston school system, he said.

News of Spillane's appointment was greeted positively by Donna Caudill, president of the Fairfax Education Association, with 6,300 members, the county's largest teachers organization. "He appeared to be very honest and open, and certainly the . . . education association will keep an open mind in dealing with all of the issues relating to him."

Spillane said yesterday he never applied for the Fairfax job, but was persuaded to consider it by Carroll Johnson of the National School Boards Association, who was hired as a search consultant by the Fairfax board.

Before going to Boston, Spillane was deputy commissioner of education in New York state for three years, and he has 12 years of experience as superintendent of school systems in New Jersey, Long Island and upstate New York.

"You must understand," he told the news conference, "my wife has some sense of humor to let us move 11 times in 27 years of marriage. The family is really looking forward to the easier winters." CAPTION: Picture, ROBERT R. SPILLANE . . . to be paid $90,000 a year; Chart, Pay and Benefits for area Superintendents: Alexandria -- Robert Peebles Salary: $69,861. Expenses: Reimbursed up to $6,000 for school-related activities. Health benefits: Standard for school employes. Perks: Use of '83 Oldsmobile. Retirement annuity; Arlington -- Charles Nunley Salary: $64,202. Expenses: $3,000 auto allowance for use of own car on business. Health benefits: Standard for school employes; District -- Floretta McKenzie Salary: $74,000 plus 3 percent bonus. Expenses: $5,000 allowance. Reimbursed for cost of attending professional meetings. Health benefits: Standard for school employes. Perks: Chauffeured '83 Ford. Annuity up to $5,000. $10,000 a year for housing; Prince George's -- John Murphy Salary: $76,000. Expenses: Reimbursed for school-related travel expenses. Reimbursed for professional meetings. Health benefits: Standard for school employes; Montgomery -- Wilmer Cody Salary: $80,000, increasing to $85,500 July 1, 1985. Expenses: Moving costs. $200-a-month expense account. Reimbursed for cost of professional meetings. Health benefits: Life insurance paid. Group medical insurance paid. Perks: Use of '83 Buick.