A parade of Fairfax County students, teachers and PTA presidents told the School Board last night that the superintendent's proposed teacher salary increase amounts to an insult that would endanger the school system's good reputation.

The teacher salary issue dominated the first of three School Board hearings on Superintendent Robert R. Spillane's proposed $589.2 million budget for fiscal 1987. Most of the county's 7,500 teachers are staging a work slowdown to protest the pay offer.

The audience of more than 200 at Luther Jackson Intermediate School applauded any speaker who denounced the proposed 4 percent cost-of-living raise. And the crowd gave a standing ovation -- accompanied by whistles and cheers -- to South Lakes High School teacher Chuck Cascio after a speech in which he said teachers were "subjugated, patronized and insulted" by the budget.

Cascio held up a poster published by the school system that says the county "applauds its teachers." "I say: Don't applaud," he told the School Board. "Just throw money."

Spillane's salary offer included less than half of the 8.8 percent cost-of-living increase teachers requested. Spillane asked for extra money for new teachers and veteran teachers, but the county's two teacher associations say that two-thirds of the county's teachers would get only the cost-of-living raise and their normal grade increase.

Spillane's budget would increase overall spending by 7.1 percent. Other big-ticket items in the budget include reducing kindergarten class size, expanding use of classroom computers, hiring more guidance counselors and providing more elementary school art instruction.

The School Board holds additional budget hearings tonight and Saturday. It is scheduled to vote on the spending plan Feb. 19, and then send it to the County Board of Supervisors, which has the final say.

Those urging more pay for teachers said teachers lost money to inflation over the last decade, are paid so little they cannot afford to live in the community where they teach, and are tempted to take jobs in private industry, where pay is better. They said the county already had trouble attracting mathematics and science teachers and that the shortage would reach other fields if pay is not increased more.

Spillane has defended his proposal, saying the increase is in line with what most workers nationwide will get this year. School officials question whether teachers have lost more to inflation than other workers or county residents.

Among those speaking were organizers of a student petition drive in favor of higher salaries; they said they had collected thousands of signatures to give to the Board of Supervisors.

Arthur L. Moshos, president of the Fairfax High School PTSA, told the School Board: "Put your money where your mouth is. Pay them what they're worth." Similar sentiments were voiced by more than half a dozen other PTA presidents. The county Council of PTAs has endorsed a higher teacher pay raise than Spillane has proposed.

A spokesman for the county Chamber of Commerce, Gene Price, said the group endorses establishment of a commission to study teacher pay scales and merit pay for outstanding teachers.