Three eighth-graders at Arlington's Williamsburg Intermediate School and one 10th-grader at Washington-Lee High School were charged with assault and battery yesterday in a series of fights in which a baseball coach and his volunteer assistant were hit, police said.

Youth Resource Sgt. David Tooley said police did not know what provoked the fights Wednesday, which started with an oral confrontation between a member of the Yorktown High School junior varsity baseball team and the three Williamsburg students.

No hearing has been set for the youths, police said. The names were not released because they are juveniles.

The coach who was slightly injured, Peter Kane, could not be reached. Neither police nor school officials would give the name of his assistant, who was also hurt.

The 20-year-old assistant tried to stop the four youths from fighting and then was assaulted by the 16-year-old brother of one of the three Williamsburg students, Tooley said.

When Kane tried to end that fight, one Williamsburg student assaulted him from behind, police said.

A similar incident last October at Wakefield High School, in which a math teacher was hit several times when he tried to break up a fight, prompted the School Board to consider revising school disciplinary policy. The board will consider changes in the policy at its meeting June 6.