The Fairfax County Board of Supervisors promised yesterday not to increase the rates of four of the county's most lucrative and unpopular taxes and set tight restrictions on how much the county and school system budgets can grow next year.

The board voted not to increase the rates for real estate and personal property taxes and two business taxes -- the business, professional and occupational license tax and corporate utility taxes -- in fiscal 1992, which begins next July 1. The board also voted to limit the increase in county funding for schools to 6 percent and to hold the county government spending increase to 4 percent.

The four taxes account for more than 80 percent of the county's local tax revenue. Vowing not to increase them when the economy is in a slump, state and federal funding are drying up and revenue growth is projected to be marginal will place the board in a tight fiscal box. If revenue projections are incorrect, the board may have to cut programs and services in an election year to balance the budget.

In a final, frantic meeting before beginning a five-week summer recess, the board also: Approved holding seven bond referendums in November, totaling almost $300 million. The referendums will seek voter approval for the county to go into debt to finance capital construction and program expansions of $169.26 million for public schools; $80 million for transportation; $21.75 million for housing; $9.5 million for human services; $8 million for sidewalks and trails; $6.72 million for storm drains and $4.57 million for public safety.

Voted 5 to 3 to authorize county staff to proceed with the sale of $330 million in so-called revenue bonds to pay for completion of the Fairfax County Parkway, formerly called the Springfield bypass. The board had previously considered financing the parkway with general obligation bonds, which would have required voter approval. Some county residents, claiming the revenue bond financing plan is illegal, have asked the Supreme Court of Virginia to block it.

Unanimously approved a new Comprehensive Land Use Plan for the county to guide future development and transportation improvements, but delayed adopting the plan's restrictions on development until next spring. Instead, the board approved "in concept" the plan's general goal to moderate development and focus it in certain areas. Proposals to reduce development in specific areas were not addressed.

Many residents and citizens groups who wanted road widenings deleted from the plan because of their potential to disrupt neighborhoods and the environment met with limited success. The board voted to remove only two: the widening to six lanes of Route 123 (Dolley Madison Boulevard) between the George Washington Memorial Parkway and the Dulles Toll Road, and the widening to four lanes of Fox Mill Road From Lawyers Road to Waples Mill Road and Interstate 66. Voted to appeal to the state Supreme Court a Circuit Court judge's ruling that the board violated the state Freedom of Information Act when it met behind closed doors last year to discuss downzoning proposals to limit development.

Approved an application by the Montessori School of Northern Virginia, near Backlick Road and Route 236 (Little River Turnpike) in Annandale, to expand its hours to offer day care before and after school. Neighbors of the school launched an aggressive campaign against the proposal because of the increased noise and traffic it could cause.

Passed a law allowing up to eight mentally disabled people and one or more caretakers to live in a group home anywhere in the county without special government authorization. The law, passage of which was mandated by the state General Assembly, strips county residents of their ability to prevent group homes from operating in their neighborhoods, which officials felt violated the federal Fair Housing Act.

Voted to appeal to the state Supreme Court a Circuit Court judge's ruling that General Assembly legislation overturning the board's downzoning in the Route 28 Special Transportation Tax District was constitutional. The board authorized an appeal on the grounds that the action was special legislation for a special district and an unlawful delegation of legislative authority to property owners in the district, who must approve any future downzoning.

Summing up the board's fiscal actions, Chairman Audrey Moore (D) said, "It was a good day." She called the bond referendums "a balanced package of needs" that, combined with the revenue bonds and budget limits, showed "the board is not going to go on a spending binge."

The budget limits and the promise not to increase tax rates come at a time when the board is under intense pressure to rein in spending and grant tax relief to homeowners. The measures also coincide with a prolonged nose-dive in the economy, meaning that the board will have little opportunity to increase spending because of expansion of the tax base from normal growth.

As County Executive J. Hamilton Lambert told the board, "Your flexibility is gone."

The board was sharply divided over whether to leave the door open for possible business tax increases. In the end, the supervisors voted 5 to 4 not to increase the business, professional and occupational license and utility taxes. Democratic Supervisors Lilla Richards (Dranesville), Gerald Hyland (Mount Vernon), Martha V. Pennino (Centreville) and Kate Hanley (Providence) voted not to ban business tax increases.

"This is not the time to send a message of instability to the business community," said Supervisor Joseph Alexander (D-Lee). "We have a very serious economic downturn."

Moore said increasing business taxes "could have a very major impact on a very delicate situation."

County spending on schools this year is about $632.2 million. A 6 percent increase would add $37.9 million to next year's spending. The county general fund this year is $621.6 million, and holding spending to a 4 percent increase would mean an overall rise of less than $24.8 million.

Holding those lines on spending increases along with additional budgetary actions, according to Supervisor Sharon Bulova (D-Annandale), chairman of the board's budget subcommittee, will enable the board to avoid a potential $65 million deficit in fiscal 1992.