Superintendent Robert R. Spillane has asked the Fairfax School Board to adjust its pension policy after learning that some school employees can receive more than 100 percent of their salary for several years after retirement.

Most Fairfax school employees, including teachers, now pay into two retirement systems -- a statewide program for public employees and a county program intended to supplement the state pensions -- in addition to Social Security.

Last March, the state increased the benefits it paid out. As a result, a teacher retiring at age 55 after 30 years may collect a pension equaling 108 percent of his average gross salary in his last three years of work. After five years, the pension falls to 65 percent, then increases to 95 percent once Social Security benefits begin.

Teachers who retire at 55 after 29 years may collect pensions equaling 101 percent of their salaries for 10 years after retirement.

"I would say it is most unusual for a public pension plan to provide in excess of 100 percent of pay," Ellen Fizer, county school system director of benefits, said yesterday. Normally, she said, public pension programs average between 75 percent and 90 percent of salary.

The president of the county's largest teachers union, the Fairfax Education Association, which represents about 6,600 school employees, favors the proposal. "I don't think that anyone at any level of responsibility would think it would be justified that any person who retired should make more than they did when they were teaching," said Mimi Dash.

Under the proposal that Spillane is asking the School Board to approve tonight, pensions would range between 71.25 percent of salary after 25 years of service to 99.75 percent of salary after 35 years' work. Current employees could choose the new plan or the old one until Jan. 1, 1991.

The state and county plans are financed by contributions from employers and employees. Employees contribute 7 percent of their paychecks for the two systems combined. The schools pay the rest.

Under the new proposal, employees' contributions will stay the same, but the school system will save about $3 million a year by cutting its contributions, Fizer said.

Rick Nelson, president of the Fairfax County Federation of Teachers, which represents about 900 of the county's 7,600 teachers, said his union opposes the reduction because it would mean a cut of 18 percent in the pensions of some teachers who retire after 1991 while not lowering their contributions.

"This will take away substantial retirement benefits from many teachers," he said. "The reason the state benefits were adjusted upward is because teachers have put in so much of their money to pay for them."

Nelson said he finds it suspicious that Spillane proposed increases in school principals' salaries next year at the same time he is proposing cuts in teacher retirement pay. "What he's doing is financing the administrative raises with retirement money," Nelson said.

Fizer said school system employees typically recoup the entire amount they paid into the retirement system, plus interest, within 18 months of retirement.