A Baltimore Circuit Court judge sentenced a city teen-ager yesterday to five years in prison for his involvement in the near-fatal beating of a Northern High School student.

Keith Rantin, 16, was one of about 15 Northern High students involved in the mob beating of Willis Reese, 16, on Nov. 9 last year. Reese, who was punched, kicked and beaten over the head with a baseball bat, suffered permanent brain damage, prosecutors said. Rantin pleaded guilty to assault Nov. 12. He told Judge Thomas E. Noel yesterday that he was sorry for the incident but that he "was not directly involved."

Noel asked him what he did wrong, to which Rantin responded, "I didn't give help. I was there, and I didn't give help."

Noel, who called the beating an act of "savagery," reacted with disbelief at Rantin's explanation.

"The first step of rehabilitating the soul is to be truthful," the judge said. "That does not appear to be the case here. ... Independent witnesses have identified you and detailed your actions."

Prosecutors said a school police officer saw Rantin pull Reese's pants and underpants off as Reese was attacked in front of the school. Prosecutors dropped attempted-murder and assault charges against three others who were indicted in the case after investigators could not locate witnesses who could identify them.

Noel said he found the attack to be especially troubling because it happened at a school.

"We fought for years just to be able to get an education," said Noel, referring to the efforts of civil rights activists who fought for the right to equal education. "Now these kids are going to school and acting like animals at school. There are people that died for our right to an education, and we use schools as a battlefield."

As Noel read the sentence, Rantin's mother wailed from the front row.

Reese and his mother, who sat near the front, were quietly escorted out of court by security officers. Neither was available for comment.