Spring is here and graduation's coming, and as every red-blooded teen-ager knows, its time to party. For that reason, the Fairfax County police chief and school superintendent held a news conference yesterday in an effort to see that the revelry doesn't get out of hand.

Col. Richard A. King, the police chief, produced some grim figures: Within two weeks around graduation time last year, he said, six teen-agers died in alcohol-related car accidents in the country. Those accidents occured, he said, shortly after the teenagers had attended parties. In the same period there were 200 car accidents involving teen-agers that caused injuries or property damage.

It's not that county officials are against parties, declared School Supt S. John Davis.

The problem, he said, is that teen-agers have "the finest communicatins systems in the world," with word spreading from one to another. The result, he said, is that a party that started with only a few in attendance can mushroom "into an uncontrollable. . . almost a mob."

Arecent phonomenon is the "field party" - a party held in an open field where the terrain places virtually no limit on attendance. But parents will open their homes for graduation parties, and those, too can be a problem.

"Large gatherings of youth" have grown in the past two years, King said, "and we've had to escalate our (police) action to control this problem."

In an open letter to parents and teen-agers, the police chief warns that when a party gets out of hand, "you may find 200 to 1,000 uninvited guests showing up at your door." When this happens there can be blocking of driveways, vandalism, disorerly conduct and assaults.

Parties can also "become life and death situations, " King said in the letter, because of the potential of severe injuries to both police and citizens.

The time to worry about all this is right now, as the 10,500 seniors at the 22 Fairfax County high schools prepare for graduation ceremonies that will be held between June 4 and 6.

Last weekend police responded to complaints about 43 parties. There were two arrests and one police officer was injured, King said.

King and Davis urged parents to limit the number of guests their teen-agers invite to a party and to call the nearest police station before the event to find out the laws regarding parties and public nuisances. King said that if police are aware of a party "the nearest police unit can appear (at the scene) and be visible."

Davis said his high school principals and counselors would be working with students, citing examples of what has happened in previous years.

Both county officials told parents - and teen-agers who throw parties without their parents - to call police "at the first sign of unwanted guests" rather than wait until there are so many party goers that "it is impossible to get down the road and even find the house" because to parked vehicles.

King said police often see familiar faces at parties, "the perpetual party goers who alway cause the problems."

"Young adults must accept responsibility and recognize the rights of others." King said. "To urinate on a front lawn or litter the highway - how can we condone, just because of graduation, that kind of unlawful activity?

"It is not the desire of the Fairfax County police department to run your child's graduation from high school by arresting him at a party, but when these large parties occur and the participants are violating the law, we cannot ignore the situation," King wrote in the open letter.

"I don't know if you can understand how it feels when a superintendent stands before 400 or 500 students and notices some vacant chairs, because they were to be occupied by one of those six who died. You wonder how many other vacant chairs there will be. I experiences that every year," Davis said.