Q. "I have some questions about the school lunch program at the school my 3-year-old daughter attends," writes a mother in Prince George's County.

"The menu, which repeats every four weeks, is the same for all children, from 2 to 15. Shouldn't the meals be different for the younger kids?

"Also, the children are encouraged to eat a little bit of vegetables or salad -- even the ones they dislike -- or 'no dessert.' What do you think of that?"

A. You're wise to be concerned about those menus you sent. There is a good deal of repetition and many mixtures, making it hard for a child to identify the ingredients. Some pre-Sevens can't bear to have one food touch another, but they will eat a stew or a soup if they can tell what each item is. a

A child should get a third of his nutrition at lunch. Although the body can compensate for several days afterward, it isn't easy to make up for five picky meals a week. A Three eats so little the calories should be first-rate.

However, the menus you sent don't look so great for a Fifteen either. A single day wasn't too bad, but the cumulative effect would be one of extra fats, extra sugar and, we suspect, an awful lot of processed food.

Names like "turkey Tetrazzini" and "chicken a-la-king" are common in, manufactured foods, and so are soups like chicken jambalaya (and chicken gumbo; chicken rice and chicken noodle). This is a bad sign.

Any refinement of a food removes some vitamins and minerals. Even if the product is enriched, not all nutrients are returned, and this may upset the balance of the food.

Also, the more food is processed, the more likely it is to contain additives. The value, and even the safety, of enhancers, preservatives, stretchers, thickeners, stabilizers, artificial colors and flavors is coming under more and more question. Salt and sugar are two additives that are usually unnecessary. Six major diseases in the country have been connected with salt, sugar and fats.

It's the sugar in your daughter's diet that troubles us the most, for sugar is practically addictive. In the menus you sent, fresh fruit was served for dessert only nine times, with ice-cream sandwiches, cookies, canned fruit, brownies, cupcakes and puddings for the rest.

On top of this, there were six days when the kitchen replaced white milk with chocolate milk, lemonade or punch. The use of any fruit drink (Kool-Aid, for example) as the only beverage is against USDA regulations in day-care and school lunch programs.

The average American eats 100 pounds of sugar a year -- triple the amount eaten a century ago -- and whether it comes from cane, corn, beets, bees or trees, it gives energy, but almost no nutrition.

The more food is refined, the less value it has and sugar -- in any form -- has very little to begin with. That's why no more than a tenth of the daily caloric intake should come from sugar -- a simple carbohydrate -- rather than the sixth we now eat. Although a tenth may seem high, remember most of it is hidden in manufactured foods, from soup to salt.

Another 40-50 percent of our energy should come from the complex carbohydrates -- fruits and vegetables, cereals and grains -- so the body can use its proteins to build and repair tissues. Fats, which are in so many foods, should give 30 percent (rather than the 38 percent we now eat) because they also give energy, and they keep hunger away longer. The first way to cut back is to quit fried foods.

And yet potato chips (6-100 caloires) were served three times, and there were French fries and hash browns. And with all these temptations your child is expected to eat French onion or navy bean soup; Brussels sprouts and broccoli; vegetable medleys and succotash, and omelets, cheese fondue and pasta cooked five ways. Ho ho.

It's counterproductive to give a child food she won't eat. As Harvard nutritionist Frederick J. Stare once wrote, "Food that is planned, but not eaten serves no use."

It isn't as if natural foods and simple menus are impossible.

Good Food, Swaim, Inc., an Arlington catering firm for day-care agencies, cooks fresh food daily and always from scratch, says owner Martha Swaim.

Milk is served daily, with fruit for dessert. The breads are dark; the rice is brown, and the pasta made of pure semolina.

The beef is hormone-free and there are no preservatives or additives in anything, except for the butter, mayonnaise and canned tomatoes, the only processed foods they use. Salt is added only to the peanut butter they make.

Swaim says she cooks the potatoes in their skins; makes the soups from a stock of bones and vegetables and fries nothing. Entrees range from meatloaf and tuna sandwiches to paella, lasagna, tacos, quiche, cassoulet and red beans and rice with sausage.

If your daughter's school uses a lot of processed food, or if the teacher says she barely touches her meats and vegetables, she should be given only healthy food at home: fresh fruit, whole grains, dried beans and proteins, rather than sweets or fried foods.

Breakfast should be an egg or hot cereal with juice. At dinner a child should taste everything in the main course, not because it's a rule, but because she is told, "This may be the day that you like it."

And yes, she should eat a reasonable amount of her meal, but for her own well-being, not for a prize. If she doesn't, you say you're sorry she's not hungry and simply excuse her from the table while you have dessert: usually fresh fruit, but occassionally something luscious.

A child stops playing games when no one else plays.

For some eye-opening information on additives, send $2 to the Center for Science in the Public Interest, Box 7226, Washington, D.C. 20044, for "Chemical Cuisine," one of their three excellent posters on nutrition.

To Dr. Mark Hegsted, director of the USDA's Human Nutrition Center, the best general advice is in the new government pamphlet, Nutrition and Your Health. It's available free from USDA, Room 6009 South Building, Washington, D.C. 20250. It tells you to eat a variety of foods -- and why. w