Timothy M. Greer, 19, a 1978 graduate of Fort Hunt High School and son of a two-star Army general, was convicted yesterday by a Fairfax County jury of helping set the fire that gutted the school last Dec. 30.

A second defendant, Robert Smithwick, 18, later pleaded guilty to arson in a separate Circuit Court proceeding. Smithwick, who faces two to 10 years in prison, has admitted he threw the gasoline-filled bottles that set the school afire.

The jury sentenced Greer to two years' imprisonment, the minimum he could have received. He will be eligible for parole in six months.

Greer's parents, Maj. Gen. and Mrs. Thomas U. Greer, were present in the courtroom and wept as the verdict was read. Their son sat impassively in front of them and later was led away in handcuffs to the Fairfax County Jail.

The jury's decision followed testimony on Tuesday by Greer's high school friend, Fort Hunt senior Matthew Musolino III, 18, who also is a defendant in the case and whom police credit with helping their investigation.

Musolino is scheduled to stand trial June 18 on a charge of vandalism, a lesser charge agreed to by prosecutors in exchange for the youth's cooperation with police.

Deputy Commonwealth's Attorney Steven A. Merril said after the jury announced its verdict that the felony conviction was a warning to other youths in the county who vandalize public property that such destruction will not be tolerated.

"When you play at these sort of stakes you face the fact that you will be a convicted felon the rest of your life," Merril said.

Defense lawyer Louis Koutoulakos said yesterday that while he felt the jury's verdict was "fair and compassionate" he did not believe the two-year sentence would deter other acts of vandalism.

"These things are impulsive and not clearly thought out. In these things, deterrence has very little value in my book," Koutoulakos said.

In court testimony Tuesday, witnesses said the fire was planned during an evening of drinking and was motivated by the youths' dislike for Fort Hung principal James E. Manning.

The blaze started in the school's records room at about 2 a.m. It caused $4 million in damage and closed the school for the rest of the school year, dislocating 1,745 students.

According to court testimony, Musolino and Smithwick, broke windows in the school near what they thought was the principal's office. Musolino said he then walked away, and that the next thing he recalled was Smithwick running past him saying, "The school's burning up."

The youths had obtained two bottles filled with gasoline and fused with rags earlier in the evening, according to statements at the trial.

Greer, who was described in court by prosecutors as the "wheel man" for his two friends who set the fire, said on the witness stand he thought the plan was a joke.

The jurors yesterday morning asked Judge Lewis H. Griffith if they could stipulate in their verdict that part of Greer's sentence be suspended. Griffith, in a written instruction to the jury, said each juror was "not to concern yourself with what may afterwards happen" to the defendant.

Under Virginia law, the judge can reduce Greer's sentence or suspend it completely, but he cannot increase it.

Defense lawyer Koutoulakos said yesterday he may appeal the conviction on grounds that the judge did not permit the jury to know that Musolino, whose alleged involvement in the arson was greater than that of Greer, he had offered 'a deal' by the prosecution in return for information about the fire.

Musolino, who testified on Tuesday that he, too, had no idea the whole school would be burned, faces a maximum of 12 months in jail or a $1,000 fine if convicted.

Smithwick, a reserve forward last season on the Fort Hunt basketball team, will be sentenced July 13. CAPTION: Picture, Fire investigators move down burned out hallway at Fort Hunt High School after Dec. 30 blaze destroyed cafeteria, kitchen and administrative offices. By John McDonnell - The Washington Post