Q. "Our daughter wants to give a party in June, to celebrate her graduation from high school," writes a father in Northwest Washington.

"However, she says if we don't let her serve beer she would rather not have a party at all, and I'm sure there will be some kids coming who are under the legal drinking age. I'm worried about both my legal and my moral responsibility.

"She also wants us to go to a movie or something, 'so we won't inhibit the kids', or at least to stay upstairs.

"Heather just turned 18 last month and she's a good kid, but I've heard an awful lot about party-crashing and wild times around here, especially at graduation.

"Am I being as old-fashioned as she says?" A. Yes, you are being old-fashioned. But then, she's being new -fashioned.

Although everyone in the family has the right to give parties in their house -- unless there's a big problem, like an illness -- it's for you and your wife to make the rules. That's one of the perks of parenthood.

There is room for negotiation, however, to combine reality with caution.

If you daughter says her friends usually have alcohol at a party, don't kid yourself: They're going to have at yours, one way or another. That's why we think you serve beer to those 18 and older and soft drinks for those under 18 and for those who don't drink.

If you only had sodas, a dozen kids would make a run for some rum or vodka to mix with them and that is much more dangerous. Liquor taken surreptitiously is likely t be swallowed much faster and it surely won't be measured.

It takes an hour for the average person to absorb the half-ounce of absolute alcoholin a 1 1/2-ounce shot of 86-proof liquor -- the same amount that's in a 12-ounce cup of beer or 5 ounces of wine -- but kids mix drinks with a heavy hand. They also have poor tolerance. Like anything else, drinking takes practice.

There's one thing you can say for teen-agers. When it comes to drinking, they're willing students.

We bet that half the 17-year-olds in the metropolitan area -- and many younger ones -- have false ID's in case they're carded in the bars. National figures certainly show that there is a great deal of drinking among teenagers. The report issued by the National Commission in the Year of the Child says that nearly on out of five teen-agers between 14 and 17 not only drinks, but has a drinking problem.

As Lt. Robert Goldstein, coordinator of the D.C. Alcohol Countermeasures Program, says, "Alcohol is the No.1 drug problem in the country." To pretend otherwise, he says, is no more than "the ostrich effect."

Although you can't change the drinking patterns of your daughter's friends by a single party, you can help them drink with reasonable safety.

When you buy beer, get the 'lite' kind, which has fewer calories because it has less alcohol, and get less than your daughter would like, since many guests will show up with six-packs.

You also want to set a 2 a.m. curfew, which is late enough to satisfy most partyers, but too late for the rest to find another place to play. And since it is unfashionable for most teen-age parties to start before 10, the drinking hours are more limited.

You should tell the police about the party, so they will drive by occasionally, and your daughter should ask your neighbors to let her know if the music gets too loud. This is not only mannerly, but it helps her realize that she has a responsibility too.

She also should put away breakables and move the better furniture out of the way.

But so far as being out for the evening -- nonsense. A little inhibition is just what you want. It's your duty to be at the party, both as a protector and as a host.

This doesn't mean, of course, that you stand around like a policeman. Instead, you or your wife just walk through from time to time, looking pleased to see your daughter's friends, checking on the drinks or the cup supply or bringing in some food: the best reason of all. You have to remember that teen-agers are usually too excited about a party to eat dinner before they go, which makes it that much harder to metabolize alcohol.

The food should be hearty -- something popular, cheap, filling, hot and complicated. Tacos, pork barbecues and sloppy Joes all require a lot of backing and forthing from the kitchen and give you a discreet way to oversee the gathering.

When party crashers know that parents are going to be around there is a lot less crashing. You also will have less trouble with guests if you establish your rules at the first infraction, rather, than the fifth. This includes, for sure, a ban on hard liquor and pot, which means a certain number of walks outdoors. Cars (like bedrooms) are off-limits at a teen-age party.

You establish rules not by saying, "See here, what do you think you're drinking?" or other war-mongering questions, but by a "Sorry, that's against the rules here." After that a very close eye is kept on that young person and any further infraction is met with a quiet and firm, "Thank you for coming," as you lead your guest to the door by the elbow. And when he objects, you keep right on leading.

A parent negotiates with his child, but not her company.

When the party breaks up, you take up a new responsibility -- a pleasant good night and a once-over to make sure that each driver is obviously capable of driving. Even though you have had to trust anyone under 18 to obey the area's no-drinking law, you -- and your daughter -- can be brought to court by a parent for contributing to the delinquency of a minor, which might happen if there were an accident.

If you have doubts, the guest can spend the night, be driven home by you or someone else, or take you up on a dare to pass the classic psychomotor test any normal 5-year-old can do: Walk a straight line, heel to toe, for 15 feet, with arms straight out at his sides and without a waver.

If a driver isn't well-coordinated enough to do this, or to say the alphabet without missing a letter, he probably has a blood-alcohol level of at least one-tenth of 1 percent and won't be able to keep his car in his own lane or turn a corner well. Because inexperience in both drinking and driving can be lethal combination, New York state cuts this limit in half if the driver is under 21, and revokes the license for a year if convicted.

We could do with a law like that ourselves.

Every year there are 50,000 traffic deaths in the country and half of them involve alcohol. Never is it more poignant than after the graduation parties in May and June when the obituary page has its heartbreaking stories of young people stopped right on the threshhold of life. There is no good time to lose a child, but surely there can't be a worse time than this.

You can't protect your daughter and her friends forever, but you can help them grow up safely -- without the ostrich effect.