Q. "My child is in the second grade," writes a Fairfax mother, "and every three or four weeks he just gets sick -- until about 10 a.m.

"Frankly, I don't think Danny is sick at all, but I hate to believe he has a psychological problem. Otherwise he seems to like school just fine.

"I really wouldn't mind him staying home once every three or four weeks, but I don't know if I should let him get away with it. Besides, it's so hard to get a sitter at the last minute."

A. Schoolitis -- probably the most prevalent childhood disease -- strikes with virulence about now, and it seems to strike the child of the working mother worst of all.

When a child suddenly covers his mouth with his hands, blows out his cheeks, gags and runs to the bathroom 20 minutes before it's time to leave for school, it's hard to know what to do.

Acutally, you have several options:

You can persuade yourself that your child is really sick and rush to the doctor for an emergency visit, where you will be put in the Sick Children's Corner, so you can both be sick next week, or

You can say, "Nonsense," and send your child, sniveling, out of the door and then fell guilty all day, or

You can let him stay home with a sitter, but in bed with no company, no television and a diet of thin gruel, or

You can mutter "What will it matter in a hundred years" and give the day to your child.

Personally, we usually choose No. 4, for the sake of the mother as well as the child. An occasional holiday soothes the soul and gives your child what he needs most: you.

Q. From Hyattsville a mother writes: "My daughter Susie (she spells it Suzi) distresses me. Until she was 3 years old my mother cared for her every day while I worked and after she moved back to North Carolina Susie visited her for two weeks every summer for years; I thought she loved Mama.

"Last year my mother had a stroke and now it's our turn to take care of her. It isn't easy -- she's in a wheelchair and rather senile -- and Susie, who is 15, is behaving terribly. She acts like she doesn't owe Mama anything.

"Sometimes she will be nice to her, but usually she just flounces around, furious at everybody. She says she is too ashamed of her granny to have anyone over any more (Mama drools a little; she can't help it) and more and more Susie just goes to her room, slams the door and turns up her stereo so loud it drowns out Mama's television in the living room.

"My husband and our 12-year-old son do what they can but I was really counting on Susie's help. Instead I hardly get any. All this tension is making me sick."

A. As admirable, and as necessary, as it is to take care of your mother, you can't assign your obligations to someone else -- even Susie. It doesn't matter if you think she owes your mother the moon. Susie is the peson who has to decice how much she has to give.

Right now it can't be much, for Susie is too mad to give, and you're the one she's mad at.

We can see why. Suddenly her grandmother decides how everything will be, just by being there. Your daughter must feel as if you've taken away her place in the family, which is bad enough, but you've also made her different from her friends. A fifteen cares so much what they think of her and tries desperately to conform. Unless the four most popular girls in the class have senile grandmothers in their living rooms, Susie is going to be embarrassed when friends visit.

What's worse, the more she loves your mother (and we bet she loves her a lot), the more guilty she is going to feel about it, which makes her angry at herself as well as at you.

It's time to recognize that every member of the family has rights -- not just Mama -- and you have to go as far as you can to insure them. We think you'll find that when you make some concessions on your mother's behalf, your daughter can make some too.

Start by looking at the situation as an outsider would.

Although your mother may be awake most of the day, she doesn't have to spend all of it in the living room.

Let Susie pick one or two afternoons a week when she knows that if she brings friends home on the spur of the moment, your mother will be in her bedroom, and the living room will look the way it used to -- without any rubber rings, tissue boxes or sick-bay paraphernalia.

Your son deserves the same privileges, unless you want him to get resentful too, and each child should be allowed to have a small party every few months, even if it does bother your mother. She can't come first all the time.

There also should be one meal a week when your mother eats and goes to bed early so you can have dinner together as a family, even if it's later than usual.

Your children aren't the only ones who need a break.

Expect them to sit for you one night a week, so you can go out with your husband; for one afternoon a week, so you can run errands, and one Saturday a month, just to do whatever you want.

You're the linchpin in this operation. No matter how great your love, you need some respites to keep up your spirits.

The children also should be expected to do more than granny-sit.

Unless it's for those parties, Susie should be expected to keep her stereo at normal levels all the time and to pitch in and help with her grandmother -- giving her a weekly shampoo, folding her laundry, or just sitting with her and letting her talk.

When Susie gets back some of the old privileges she took for granted -- and maybe a few more -- she won't feel so displaced. This should make a lot of the tension disappear.

Parents Alert:

Every now and then something dandy is done for that most neglected age, the 6-to-12-year-olds. With a flourish of trumpets we present "Free Stuff for Kids." For $2.95 this Meadowbrook Press book lists dozens of things a child can order free, a number of others that cost from 10 cents to $1, and all with such simple instructions a child can mail the requests without your help.

In weeks the postman will deliver all the information a child should need to make paper; fix a bike; find a pen pal; catch a fish; build a campfire; make a camera; win at chess; get a cricket (magazine) or knit a scarf. And more.

With so much mail, Christmas won't seem so far away.