Supporters of Arlington's school system packed a public hearing last night to urge the County Board to support the School Board's budget for the next fiscal year although it exceeds the county's recommended spending guidelines.

Dozens of residents wearing yellow "Invest in Education" signs told the County Board that extra funds were needed to improve the instructional program and raise teacher salaries as one way to offset predicted teacher shortages.

The County Board finances the bulk of the school budget, but cannot tell the School Board how to spend its money.

The school advocates were among about 200 people who attended the County Board's hearing last night at Kenmore Intermediate School on the proposed county and school budgets, on which the County Board will act April 27.

The proposed county budget calls for $260.9 million, of which $215.3 million would come from the general operating fund, supported largely by real estate taxes. Since the county is facing a projected $6.3 million surplus, some speakers asked the County Boardlast night to cut the real estate tax rate of 97 cents per $100 assessed value. Board members have said they may cut that rate on Saturday.

School supporters suggested last night that some of the expected surplus be used to increase the school budget over the $74.3 million budget the School Board has requested, which calls for a county contribution $2.8 million greater than the county's guideline.

Speaking before the hearing of expected support for extra school funds, County Board Chairman John G. Milliken said, "I'd like to try to do it. I'm not sure we can." He added the two boards "would try to work it out together."

Among the nonschool spending requests were calls for more funds for senior citizens' and day-care centers, adult literacy programs, and social service programs to help refugees and the physically and mentally handicapped.

While there was also a number of requests for the county to seek ways to increase the housing supply for low- and moderate-income persons, a large contingent of residents from the Westover community in northwestern Arlington objected strongly to the proposed use of $500,000 in community development funds to renovate the 152-unit Westover Apartments.

Opinion in the Westover area appears to be split on the plan of the Arlington Housing Corporation to buy the complex with the aid of almost $6 million in tax-exempt bonds. After county residents rejected an Arlington public housing authority, the county signed an agreement with the Alexandria Redevelopment and Housing Authority for its assistance in financing privately undertaken renovations of housing complexes in the county.