A 16-year-old Woodbridge youth, critically injured in an automobile accident in Prince William County Thursday afternoon, died yesterday, officials said, becoming the fourth student or recent graduate of Stonewall Jackson High School to die within 11 days.

Billy Horton, of the 4500 block of Kentmore Drive, was driving east on Davis Ford Road near Oakhurst Lane about 5:30 p.m. Thursday when his car crossed the center line and struck two cars coming from the opposite direction, police said. Horton, a junior at Stonewall Jackson and a member of the school's football team, was not wearing a seat belt and was thrown from his vehicle, officers said.

Horton died yesterday morning at Fairfax Hospital, officials said. The other drivers were not seriously injured, according to police.

The cause of the accident was under investigation.

On Sept. 22 a senior at Stonewall Jackson died of a cerebral hemorrhage and a 1986 graduate of the school, which is just outside Manassas, died of bone cancer. Three days later, a 16-year-old junior at the school collapsed at a party and died a few hours later. An autopsy has not yet been completed.

Counselors at Stonewall Jackson, where a crisis plan was implemented this week, called in five school psychologists yesterday.

"All the counselors were pretty drained from dealing with everything last week and this. We just had to bring in more people," said William Wood, guidance director.

Wood said the psychologists and the school's five guidance counselors spent the day working with students. "No sooner would we get through with one than we'd have another," he said.

Horton was a defensive back on the school football team, and last night, when the team played Potomac High in Dumfries, each Stonewall Jackson player had Horton's number -- 32 -- taped on his helmet.

"We had a team meeting in the morning," said Coach Jim Powell. "We talked about his death in the locker room after practice and before the game. The players are shocked and in disbelief, but they elected to play."

Principal Michael Campbell said a memorial service for all four students will be held Tuesday.