More than 300 parents petitioned the Loudoun County School Board last week, asking the board to revise its busing policy so that pupils through the fifth grade would not have to walk to and from school.

The protesting parents say they are concerned about the safety of their children, some of whom walk up to a mile to school. Leesburg resident J.B. Anderson, one of two parents who presented the petition to the School Board, said, "I just don't think 5-, 6- and 7-year-old children have got the maturity for walking to and from school unescorted, especially crossing streets."

The present school policy requires kindergarten children living within eight-tenths of a mile of school walk to school if they attend morning sessions, and home from school if they attend afternoon sessions. Those at morning sessions are bused home and those at afternoon sessions are bused to school.

First-graders who live within eight-tenths of a mile of school must walk; second- through fifth-graders living within one mile of school must also walk. Sixth- through 12th-graders living within 1.5 miles must walk.

Exceptions are made when children would have to cross streets or highways with heavy traffic, according to Robert A. Devers, Loudoun's director of transportation.

Anderson, whose 5-year-old son is driven to Catoctin Elementary by his father or another relative, lives in Prospect Hills. Other areas where parents signed the petition are Crestwood, another Leesburg development from which children attend Catoctin, and Hamilton and Sterling.

Mary Ruth Durbin has a daughter who attends Rolling Ridge elementary in Sterling. Although Durbin's daughter is driven to and from school, she would otherwise have to cross several streets and walk along a path two feet from busy Sterling Boulevard, Durbin said.

"I would not permit her to walk . . . with all these child molestings and abductions; I think the School Board has to look into these things, too," Durbin said.

Durbin said she believes that many parents have privately opposed the policy since its establishment in 1977, but that her recent efforts to have the policy changed have encouraged the parents to join in petitioning the School Board.

The School Board's policy committee will discuss the petition at a meeting Nov. 6. Committee Chairman John W. Brown said the policy was based to a large degree on economics, because it would cost more to bus every student to school, and also on the theory that it is beneficial for children "to learn to take care of themselves in walking short distances."