Rebuffed by the Virginia Supreme Court, a Manassas woman said today she will begin an economic campaign against Prince William County schools in an effort to win free textbooks for all public school students in the county.

Antoinette M. Foster said in an interview that she plans to appeal the court's rejection of her lawsuit challenging the Northern Virginia county's policy of "renting" the books to students.

Foster said she will urge federal employers in Prince William not to return school census forms to the county next fall, an action which she said would "deny the county more than $2 million in federal impact area school aid."

The federal government makes the impacted area payments to offset the costs of educating children of U.S. employes.

Foster said she considered a campaign to encourage the withholding of census forms last year, but postphoned ti to give the state Supreme Court a chance to consider her appeal.

Acting as her own lawyer, Foster argued unsuccessfully in the state courts that the guarantee of a free public education in Virginia's Constitution is contradicted by another provision permitting cities and counties to charge text rental fees to families able to pay them.

She also contends the renting practice violates the equal protection provisions of the U.S. Constitution by levying the textbook charge on some-but not all-parents.

Most cities and counties in Northern Virginia provide free texts to all pupils. Prince William, however, provides free books only to children of parents who declare they cannot afford the fees.

Proposals to furnish free textbooks throughout the state have been defeated in recent sessions of the Virginia General Assembly. In the last session, however, the legislators approved a bill providing free books to all first-grade pupils from families who qualify for federal food stamps.