A Fairfax County Circuit Court judge yesterday sentenced two tennagers convicted of setting the Fort Hunt High School fire to one year in prison, 3,000 hours of volunteer community work and $10,000 in financial restitution.

Timothy M. Greer, 19 of the son of a two-star Army general, and Robert Patrick Smithwick, 18, who threw the gasoline bottle that gutted the school, causing $4.5 million in damages, were convicted May 31 on a felony charge of malicious burning. Each will be given 10 years in which to pay the $10,000.

Judge Lewis H. Griffith, who imposed the sentence, ordered the youths to find jobs and make restitution from their own employment. Smithwick and Greer will be required to do six hours of volunteer work daily in a home for the aged and disabled after their regular work hours.

Under the order that they do volunteer work five days a week, it will take slightly more than two years for them to complete that portion of their sentence.

Both elements of the sentence were developed by Griffith with the help of Dr. Jerome G. Miller, an expert on juvenile corrections and director of the National Center on Alternatives to Institutionalization.

The sentence is designed to "adequately account for all of the defendant's daily hours," Miller said yesterday. Both will receive regular counseling, and their progress will be checked monthly, Miller said.

Sentencing for the third defendant in the case, Matthew Musolino III, 18, was continued yesterday until Aug. 3 Musolino was allowed to plead guilty to a misdemeanor charge of estroying private property June 18 in exchange for providing evidence that helped prosecutors close the case against his two friends.

Smithwick and Greer have been held in Fairfax County jail since early March, when they were charged with offenses unrelated to the arson while free on bond in the Fort Hunt case.

Griffith said yesterday the two will receive credit for the four months spent in custody and will be eligible for parole in two months.

Smithwick pleaded guilty in April to petty larceny in the theft of a tool box and was sentenced to 60 days' imprisonment with 30 days suspended. Griffith will decide later whether that sentence will be served and if so, when.

Greer received a one month sentence and a $100 fine after he was convicted in March of driving a car across the lawn of a home belonging to a Fort Hunt High School assistant principal. That jail term remains to be served.

Griffith yesterday called the Dec. 29 fire, which closed the school for the remainder of the school year and dislocated 1,728 Fort Hunt students, "an offensive criminal act of irresponsible individuals."

At Griffith's order, Smithwick and Greer, clad in sport coats and ties, were brought to the courtroom early yesterday and sat between two handcuffed prisoners appearing in separate cases.

"It was no accident that you were brought into this courtroom early to watch the sentencing of other defendants," Griffith said.

"I hope that the experience has impressed you with the manner in which an individual gets his life in such a state that he no longer has control over it. You are in such a situation now," he said.

"Does Fairfax County need to be protected from individuals that firebomb its buildings? And what if someone had been inside the school, or if firefighters had been injured in combating the blaze? You may well have stood before this court on a charge of murder."

Griffith's lecture was preceded by three hours of frequently heated debate between Fairfax prosecutor Steven A. Merril, who argued for two years in prison - the maximum sentence - and Greer's attorney, Louis Koutoulakos. Koutoulakos accused Merril of being a "bloodthirsty" prosecutor, after which the judge cautioned Koutoulakos against "snide remarks" against the prosecutor.

Koutoulakos and Stefan C. Long, Smithwick's attorney, argued that both defendants had been sufficiently punished by their four months in jail and that further time in jail would be inappropriate.

County probation officer William T. Hauser agreed, saying the sentence should be limited to volunteer work and financial restitution. But Griffith disagreed.

Before the sentencing, Greer's father, Thomas U. Greer, testified in solemn tones that his son had "matured three to four years in these months of jail. He hasn't complained, and he is deeply concerned at the manner in which this was affected his mother and family."

Long said later that volunteer work and restitution are no unique but are seldom sought by defense attorneys in Fairfax County.

"It's the result of a 1977 Virginia statute," Long said, "that states that some plan of restitution is required in cases involving properly damage if the defense is arguing that some or all of a sentence should be suspended.

"Quite frankly, it would have been easier for these kids just to go to jail."