ALEXANDRIA, Va. — Four families filed a federal lawsuit against a northern Virginia school district claiming that their civil rights were violated when school officials removed bricks engraved with crosses from a walkway at a high school.

The families had purchased the bricks as part of a fund-raiser run by the parents group at Potomac Falls High School in Loudoun County. Each brick was inscribed with their children's names and the Christian symbol and donated for use on the walkway.

In a lawsuit filed in U.S. District Court, the families said the walkway became a public forum for expression when school officials allowed parents to put symbols on the bricks they had purchased. The school's removal of the bricks etched with crosses abridged the families' free-speech rights, the lawsuit argues. The lawsuit also names School Superintendent Edgar B. Hatrick III and Potomac Falls Principal E. Wayne Griffith.

Parents paid $50 to buy a brick for a walkway around the school's flagpole, and for an additional $5, could have it engraved with a symbol. An order form sent home to parents offered the choice of 23 symbols, ranging from a soccer ball to a cheerleader to the cross.

Earlier this year, school officials removed six bricks inscribed with crosses after a parent complained that he was offended by the religious symbol.

Loudoun County has been a battleground for church and state clashes in schools before. A Potomac Falls High School student was among seven students who unsuccessfully challenged Virginia's law requiring schools to observe a daily minute of silence. In February, a federal judge ruled against a Loudoun parent who argued that the Pledge of Allegiance is a prayer and that his children should not have to hear it each day in school.

Teri Nickerson, a plaintiff in the lawsuit filed on March 24, said she and her husband were upset that school officials had removed the brick they bought for their daughter Nicole, a senior. Nickerson said the brick had been in place since at least September 2001.

"We've turned intolerance around. It's no longer about the rights of the many. It's about the rights of the few," she said.

The parents are represented by the Rutherford Institute, a Charlottesville-based civil liberties group.

Hatrick said he had the bricks removed because the school system's lawyers advised him that it would be illegal to allow them to remain as part of the permanent infrastructure of the school.

"It does not matter if 100 people complained or just one," he said. "It depends on whether we think we're doing something against the law."