The chairman of a group of 21 Northern Virginia school superintendents called on the legislature last night to increase the state sales tax by 0.5 percent to help offset sharp cuts in state education aid expected next year.

The plea came from Arthur W. Gosling, superintendent of Arlington schools, before an audience that included legislators who warned that a tax increase has almost no chance of enactment at the General Assembly session that convenes next month.

Gosling told the legislators, municipal officials and superintendents that any cuts in state aid to school systems in the region would have direct impact on students. "We are going to hurt the children," he said. "We don't have fat in our budgets."

Because education is so essential, Gosling said, the state could earmark for education any money raised by increasing the 4.5 percent sales tax.

"New revenue sources have got to be found," he said. "We would like you to think about a bigger pie."

Gosling spoke at the Westpark Hotel in Leesburg to a meeting of the Region IV Superintendents Study Group, school officials from 15 counties and six cities in the northern quarter of the state who meet regularly to discuss education issues.

Legislators and municipal officials were asked to join the group for the first time last night because of the financial squeeze expected from the state.

The meeting also came a month after a proposal that the state transfer as much as $85 million in education aid from some affluent Northern Virginia systems to poorer systems downstate.

Under that plan, developed by a panel appointed by Gov. L. Douglas Wilder (D), Fairfax County would lose $64.9 million in the two-year budget that takes effect July 1, 1992, Arlington would lose $9.3 million, Alexandria would lose $5.5 million and Loudoun County would lose $4.6 million.

"We should not diminish one to help the others," Gosling said.

School officials applauded the idea of a tax, saying it would be a way to increase the pool of education funding.

Warren Pace, superintendent of Falls Church schools, called it a great idea, saying his schools would lose $710,000 under the plan to reallocate state aid.

But legislators said it would have almost no chance of passing when the legislature convenes next month.

"In 1991? Poor to nil," said state Sen. Charles L. Waddell (D-Loudoun). "It's election year for 140 legislators."

Del. Linda Rollins (R-Leesburg) said she supports the idea of raising money for education, but doesn't think its time has come in a tax-shy Richmond.

"I don't think that's going to happen," Rollins said. "I think that they {school systems} are going to have to find ways to cut back."