The Arlington County Board last night approved spending guidelines for the next fiscal year that call for no increase in the real estate tax rate, but allow a 2 percent increase in school and county budgets.

The guidelines do not address salary increases for county and school employes because County Manager Larry J. Brown will not make his recommendations on pay raises until early next year when financial projections are refined for fiscal 1987, which begins July 1.

The spending guidelines traditionally are adopted this time of year to give the county and school financial staffs direction in preparing budgets for adoption by the School Board in February and the County Board in April.

But this year the School Board balked at Brown's suggested guideline of $59.6 million, a $600,000 increase over the current year. Superintendent Arthur W. Gosling has projected that the schools may need at least $1 million more than that to make program improvements requested by the board.

School Board Chairman Gail H. Nuckols, backed by school activists, told the County Board last night that her board wants to develop a proposed budget based on the school system's needs and would use "reasonableness" as a guide.

The County Board agreed with that request after lengthy discussions about the negative public perceptions attached to "guidelines." Instead, Brown is to develop a county budget that, for his planning only, uses the $59.6 million figure necessary just to maintain current school programs and mandatory cost increases. Other school needs will be factored into the school budget as it is developed.

As adopted last night, the guidelines call for a county budget of $224.4 million that would include $126.4 million for county services; $59.6 million for the schools; $10 million for the county's share of the Metro transit system operations; $14.5 million for debt service and a $2 million contingency fund.

The guidelines also establish capital projects funds of $7.6 million for the county and $1.3 million for the schools. The remaining $2.5 million is for the community activities fund, which finances facilities jointly run by the county and schools.

The county staff's initial forecasts indicate the county is entering robust economic times, largely because of the countywide boom in economic development, said Mark Jinks, the county's budget director.

"We are projecting a very healthy Arlington economy," Jinks said before the meeting, citing the planned opening next year of the 100-store Ballston Common shopping center.

Based on the current real estate tax rate of 95 cents per $100 assessed value, the county staff is predicting that revenues next year will total $230.2 million, in part attributable to a projected increase of at least 8 percent in the real estate tax base.

The county is beginning its budget process this year with an expected "surplus" instead of a deficit because the costs of operating county and school services are expected to be $224.4 million -- or $5.8 million under projected income.

That money could be used for program improvements or employe pay raises; a 1 percent salary increase for both county and school employes costs about $1.4 million.