A Fairfax County juvenile judge, rejecting claims that racism played a part in the case, yesterday placed a 13-year-old student on 12 months' probation for knocking a teacher unconscious after she slapped him.

"The court feels . . . that you were clearly wrong, that you were clearly the aggressor," Judge Gaylord L. Finch Jr. told the youth during a hearing in Juvenile and Domestic Relations District Court. "I don't think it was an assault, I think it was a massacre."

Stephanie Weddle, a teacher at Walt Whitman Intermediate School, was knocked to the floor by the youth and received facial fractures during a confrontation over his cutting into a lunch line.

School officials said Weddle was disciplined for violating school policy by slapping the student in the face but would not say what measures were taken, because personnel information is privileged.

That Weddle, who is white, was disciplined, while the student, who is black, was found not innocent of assault prompted complaints from the NAACP and others that racism was a factor in the decision to prosecute the youth for an incident they contended was precipitated by the teacher.

Assistant Commonwealth's Attorney Scott Smeal told the judge there was no evidence that racism played any role in the case. "It's unfortunate that the allegations of racism clouded the issues of school discipline and individual responsibility," Smeal said after the hearing.

But the youth's attorney, Inga Watkins, called the sentence, which included 100 hours of community service, "too severe." Said Watkins: "I do feel the whole series of events . . . may have been different had he not been black." The maximum penalty for assault and battery, a misdemeanor, is a year in jail and a $1,000 fine.

Watkins stressed that racism was not a factor during the confrontation, which she described as a situation in which both teacher and student "lost control of themselves."

The racism was "perhaps more covert," Watkins said after the hearing. For example, she said, Weddle had testified during the adjudication hearing that she had felt threatened by the student.

But probation officer John A. Tuell, who prepared the presentence report, testified that the teacher felt threatened because she is 5 feet 2 inches tall and weighs 120 pounds, whereas the 13-year-old is 6 feet tall and weighs 180 pounds. After investigating the incident, Tuell said he concluded it was an "egregious act" and that the student had hit the teacher with a closed fist, not an open hand as he had maintained.

School official Nellie B. Quander said during the hearing that she wondered why the teacher continued to scold the student if she truly felt threatened by him. Quander said she had "serious concerns" about a teacher hitting a student.

Before the confrontation, Weddle questioned the 13-year-old about cutting into the lunch line and ordered him to give her his lunch tray, which clattered to the ground, Quander said. When he refused to pick it up, she waved her finger in front of his face in a scolding fashion, and he shoved her hand away, Quander added. Then Weddle slapped him, and he struck her back.

Tuell told the judge he was concerned that the youth, who had been disciplined by school officials on several occasions, did not realize it was his actions, not racism, that initiated the incident.

Under questioning from Watkins, the youth, sitting at a table in front of the judge's bench, said that if it happened again he would "obey" the teacher. He added that "it happened so fast . . . . "

Weddle was not present at yesterday's hearing and could not be reached for comment.

Juvenile court hearings generally are closed to the public to protect the identity of young defendants. Finch opened yesterday's hearing on the conditions that both the family and the prosecution approved and that the press not use the youth's name.

Finch told the youth, who is transferring to a new school next semester because of the incident, that he would never have dreamed of hitting a teacher when he was in school.

The judge noted that the youth had a lot of potential but that he must have lost respect for teachers "somewhere along the way." He then imposed the sentence recommended by the prosecutor.

"I'm sorry that this racial thing got into it," the judge said. " . . . Race has nothing to do with it."