A Fairfax County elementary school band instructor was arrested after he allegedly showed sexually explicit photographs of boys to an undercover investigator, Fairfax County police reported yesterday.

John P. Knapp, 41, who taught band at five elementary schools in the West Springfield area, was charged Thursday afternoon with possession with intent to distribute sexually explicit items involving children, officials said.

Knapp, of 10674 Myrtle Oak Ct. in the Burke area, has been with the schools for seven years, and will be placed on administrative leave until the charges are resolved, school spokeswoman Dolores Bohen said.

He was a band instructor at Keene Mill, Cardinal Forest, Hunt Valley, Rolling Valley and West Springfield elementary schools, and had taught at Fairfax and Jefferson high schools, Bohen said.

Police said Knapp was arrested at a Fairfax shopping mall. They said they seized more than a dozen items at Knapp's town house, including magazines and films, as well as various devices.

Last summer, the school system came under fire when Arthur S. Pomerantz, a former school psychologist, was charged with sexually assaulting boys.

It was revealed that school officials had been informed that Prince William County police had investigated Pomerantz years earlier but had taken no action.

Knapp, who could not be reached for comment, was released on $10,000 bond. If convicted, he could face up to 10 years in prison.