Conceding it didn't know how much Virginia spends to educate handicapped children, the State Board of Education voted has to appeal a federal court ruling that directs the state to provide private schooling, if necessary, for poor, handicapped children.

"I guess the cold news of an appeal would indicate that we are against giving each child an equal opportunity of an education," said Board President Vincent J. Thomas of Norfolk. "But that's not the case."

Thomas and other board members said one reason for planning an appeal was that the three-judge panel that ruled against the state Wednesday would be more likely to grant the board a postponement of the order's effective date. Under court rules, the state has a 90-day period in which it can appeal.

The court, however, had given state officials only 30 days in which they were to return to the court with a plan to implement the court order. State School Supt. Walter E. Campbell told the board Friday he didn't believe that state could meet that deadline because details of a federal law that provides some funds for educating handicapped children will not be released in 30 days.

Another reason for seeking the delay, suggested Walter H. Ryland, an assistant attorney general, would be to gain time "to think about the costs" of implementing the court's decision. But, neither the board nor officials of the State Department of Education could later come up with a more precise estimate of what the state is currently spending to educate an estimated 90,000 handicapped children in the state.

"We just don't have the information this morning," Deputy State Supt. William H. Cochran told board member Preston C. Caruthers of Arlington. Caruthers had told the state officials that they should develop a cost estimate more accurate than an "estimated" cost of $129 million a year, which Cochran offered.

Despite the uncertainty over the costs, board member Elizabeth G. Helm of Winchester boasted Friday that Virginia's plans for schooling handicapped students "were much further ahead than were (those of) a number of states." In their order, the judges directed the state to provide "an appropriate private education . . . commensurate with the education available to the more affluent handicapped children."

Thomas said the court's order contained "stiff requirements" that would be "very difficult" to reach." But he said the state was "moving in the direction of" the court's order.

Later in its meeting Friday, the board was warned that state school enrollment projections indicate that the number of school students will drop 17 per cent by the 1985-86 school year from the record 1.1 million enrolled in 1975-76.

Assistant Supt. R. L. Boyer told the board that the projections, if correct, could lead to teacher layoffs, school closings and even problems funding teacher pension plans. Caruthers told the department staff they should "immediately" send warning letters to local school boards, cautioning them about new building programs and hiring new staffs. "They have got to be very cautious," he said.

The board was also told that a plan to require graduating Virginia high school students to pass a state examination before they get their diplomas won't be implemented before the 1983-84 school year. The requirement had been scheduled to go into effect July 1, 1978, but state officials said that would not give local school boards enough time to prepare testing procedures.

"More importantly," according to a memo to the board, some students affected by the standards "are too far along in school for effective remediation."