A Fairfax judge ordered all three youths accused of arson in the $4.5 million fire that closed Fort Hunt High School jailed yesterday, saying that at least two of them had become "a danger to the community."

General District Court Judge Martin E. Morris revoked bond for Timothy Greer, 19, Robert Smithwick, 18, and Matthew Musolino Jr., 18, in the wake of a weekend incident allegedly involving Greer and Musolino and the arrest of Smithwick on Tuesday night on grand larceny charges.

Smithwick was arrested at his Candlewood Drive home in the Fort Hunt section of the county and charged with taking a tool box from a truck parked in front of a restaurant on Feb 4.

Both Greer and Musolino were arrested early Saturday morning and charged with allegedly driving a car across the front lawn at the home of David B. Budd, an assistant principal at Fort Hunt High.

"Rm. Greer, I find that you are a danget to the community and I revoke your bond," Morris told the 1978 Fort Hunt graduate yesterday. Then, turning to Musolino, a starting fullback on the school's football team, Morris said: "Mr. Musolino, If find that you ... also a danger to the community and I revoke your bond."

Smithwick, detained without bond since his arraignment on larceny charges early yesterday, had agreed he would continue to he held without bond.

Throughout yesterday's hour-long proceeding, Morris made clear his unhappiness at the three youths' recent brushes with the law. I went out on a limb for these two boys," he said, referring to Greer and Musolino. "Now I'm going to keep my thumbs on them."

Morris released all three on bond on Jan. 8 after telling the fathers of Musolino and Greer, who accompanied their sons to court, that he wanted them kept under close supervision.

Yesterday Morris told prosecutors to prepare an order by April 5 requiring Major Gen. Thomas U. Greer and Mattew Musolino Sr., the boys' fathers, to show cause why they should not forfeit their sons' $5,000 bonds.

Attorneys for both Greer and Musolino waived their clients' preliminary hearing yesterday in the arson case, a step already taken by Smithwick. That action means that prosecutors will seek indictments against all three when the grand jury meets March 19.

Yesterday, attorneys for Greer and Musolino sought to portray last Saturday's incident as a spur-of-the-moment prank that ended in Greer impulsively, and without consulting Musolino, driving his car across the lawn of Budd's home on Oaklawn Drive.

That picture immediately was challenged by assistant Commonwealth's Attorney Steven A. Merril, who said the two had been returning from a party when the incident occurred.

Merril said the two were apprehended by county police who were staking out the home at the time. Budd has complained that his home has been vandalized repeatedly in recent months.

Budd, who sat through yesterday's hearing, has estimated that the latest incident caused about $500 in damage to his property.