HAVING CHILDREN is not, Miss Manners would have thought, a competitive sport. And yet there are so many parents who go in for it as such that she hopes they will at least gain the experience to teach their children the mannerly way to handle competitions.

Your truly competitive parent loses no opportunity to enter his child into competition, beginning with its birth weight. One measures the child's performance against charts and live competitors -- including those available in the hospital nursery, the other products of one's childbirth class, the memories of former champions, and total strangers who are minding their own business, taking the air in their carriages and strollers at parks and zoos.

What the child eats, when he performs certain actions or pronounces new words, when he learns not to perform certain actions -- every detail can be used to check the child's rating against the competition. It does not sound to Miss Manners like an entertaining or useful sport, but, then, tennis sounds foolish, too, when its rules are explained to a nonparticipant.

The time comes, however, when the child is inevitably pitted against others, for academic or athletic tests, for spots in classes, teams, plays and other prizes and honors of the society. He must therefore be taught to be a brave loser and a graceful winner.

The basic attitude to be taught is that there are enough goodies in the world for everyone to be blessed (although the distribution system may be somewhat slow and haphazard), so that one must be pleased at the success of others even if that seems to delay one's own triumph.

The illogic of this position, flying in the face of the simple fact that you got what I wanted, is apparent to the tiniest child. Nevertheless, it is one of the tenets of civilization, and subscribing to it produces first nobility and then happiness.

Let us say, for example, that your child tries out for the part of the prince in the school play, as does his best friend, who gets it. Your child doesn't get a lesser part, either, but is told that being an usher is just as important as being a star.

Having wished his rivals to be run over on their way to the audition, the child is now furious at 1) his friend, 2) the teacher who distributed parts and 3) fate, in that order.

He is behaving naturally, but not civilly. By citing the litany, one must persuade him to:

Wish the others success beforehand with some degree of plausibility, which does not include saying sullenly, "I just know you'll get it, I just know you will."

Compliment others on their attempts, regardless of whether one considers them to have messed up or to have been threateningly good.

Make his best try, measuring himself against his own ability, not against the probable achievements of others.

Congratulate the winner with some heartiness ("That's great, you really deserve it"), no sarcasm ("Well of course you were picked--you always are"), and no bitterness ("I didn't want it anyway").

Should your child be the winner, he must still encourage and compliment the others, but with more subtle delivery (acting ability is why he got the part, isn't it?) that excludes a triumphant tone. The correct comment to make when others acknowledge the victory is "Yes, I was really lucky this time."

Any child can learn this valuable technique. Whether a competitive parent can, when informed that a younger child than his is doing calculus while his child is still trying to figure out how to get his thumb in his mouth, is another question. MISS MANNERS RESPONDS

Q. I'm preparing for my first formal dinner party. How many menu cards are appropriate? One per guest? Fewer? I'll be seating six people, and I'm studying calligraphy.

Do you have any menu suggestions for foods that a teen-ager can be trusted alone with in the kitchen? It seems silly to have my stepson serve as footman if I still have to be in the kitchen with last-minute food preparations. I'm sure he can handle the soup, seafood mousse, salad, sherbert and dessert, but the meat course really has me stumped.

A. Actually, you need only three menu cards, as it is customary to place one between two people, so that one person can say, "What is this, veal? I can't quite make it out" and the other can lean over so that their hair touches flirtatiously as they examine the card. However, if you don't think they would enjoy that, or if you would enjoy showing off your calligraphy, you can certainly put one in front of each guest. If they quietly slip these into pockets and purses after the meal, to keep as souvenirs, you are supposed to be flattered.

Miss Manners wouldn't trust anything in the kitchen with a teen-ager, including the extra napkins. That is not to say that teen-agers do not make excellent footmen -- only that the food should be plentiful and presented so that surreptitious bites can be taken from it in the kitchen without spoiling the effect. Thus, that veal, or beef or whatever, should be cut up into a sauce and sitting in a pot on top of the stove, where it can easily be warmed up (and plundered).

Q. How can I get the person who works next to me, who has a terrible cold, to go home instead of staying around and infecting me?

A. Sympathetically. "My, you really ought to take care of yourself. Why don't you go home -- it's really more useful here if you get over it and are able to come back to work, all well, especially since I may be out next week because I think I'm catching it from you."