Jason W. Knight struggled yesterday to explain to a judge and courtroom of teenaged peers the "spur-of-the-moment" rage that resulted in a two-day rampage at Richard Montgomery High School that caused more than $500,000 worth of damage in February.

"I have hurt so many people," Knight, 19, said in a disjointed statement at a sentencing hearing before Montgomery County Circuit Court Judge DeLawrence Beard.

"I'm sorry it was my school," said Knight, who dropped out of Richard Montgomery in the spring of 1989. "My heart wasn't in it. It could have been any place. People talk about their high school years all their lives. I really don't understand."

Moments later, saying the dimensions of the crime required a tougher sentence than that recommended under state sentencing guidelines, Beard ordered Knight to serve 18 months in the county jail. He also placed Knight on two years' supervised probation and ordered him to undergo counseling.

Knight, the son of a police officer killed in the line of duty, pleaded guilty Oct. 1 to two counts of malicious destruction of property and one count each of attempted arson and of breaking and entering.

Some Richard Montgomery students said the sentence was too lenient. "He not only destroyed the school, he destroyed the people in it, too," said Thu Nguyen, a ninth-grader at the Rockville school.

Police said Knight and an accomplice, Stephen Bonner, entered the school illegally on the night of Feb. 24 and set 10 fires. In addition, police said, the pair smashed windows and furniture and opened science labs' gas jets, an action that could have caused an explosion with the flip of a light switch.

Authorities said Knight and Bonner returned the next night to demolish computers and a television studio and to burn library books and card catalogues. Damage estimates range from $533,000 to $650,000.

Bonner, who was 17 and a senior at Richard Montgomery when the vandalism occurred, will be sentenced Thursday. He has pleaded guilty to the same charges as Knight.

Defense attorney Myra Kovach said the crimes stemmed from Knight's pent-up anger and frustration in a dysfunctional family. But student Danni Pogan, 14, said Knight's vandalism "teaches us we have to deal with aggression in a different way. We should not hurt an entire community to get our hurt out."