A 14-year-old Northwest Washington boy was fatally injured yesterday as he was riding his bicycle to Parkmont Junior High School for the first day of school this fall, D.C. police reported.

Police said Robert Andrew Pellaton, of 5717 33d St. NW, tried to squeeze between a Metrobus stopped at the curb lane of Wisconsin Avenue near Cathedral Avenue and a flatbed truck, when the traffic signal turned green and the truck pulled out.

The boy was trapped between the vehicles and crushed by the truck's rear wheels, police said. The accident occurred at 8:45 a.m.

A nurse and a doctor passing by stopped to help the Pellaton youth until an ambulance arrived to take him to Georgetown University Hospital, where he was placed on a life-support system. He was pronounced dead of a skull fracture and other injuries at 9:30 a.m.

No charges were placed against the truck's driver, a 21-year-old Silver Spring man, police said.

The victim was the son of Robert A. and Lynn Pellaton. Pellaton is a teacher at Parkmont, a new private junior high school at 1640 Wisconsin Ave., NW. Mrs. Pellaton is a Montessori school teacher.

Pellaton was the third child killed in a District of Columbia traffic accident this week, and the city's third bicycle fatality of the year. There were no bike deaths last year, police said.

Police said two children were killed Sunday when they were struck in separate accidents after running from between parked cars. Michael Duncan, 3, of 1775 Trenton Pl. SE, was killed when he was struck by a van driven by Wallace G. Higginbotham, 31, of 4710 23d Pkway., Temple Hills. Higginbotham was charged with driving while intoxicated, police said.

Later Sunday, Anthony C. Thorne, 6, of 5010 Sheriff Rd. NE, was struck by a car near his home. The Thorne boy died Wednesday.

Police said there have been 44 traffic deaths in the District this year, compared to 42 at this time last year. Of those, 23 victims have been pedestrians.