Q. I am worried about my son. He is 12 years old and has no friends. He is in the eight grade at a private school, does okay in his school work (although he should be doing better), has a paper route carrying a small local newspaper, is in Boy Scouts, attends religious education classes and has certain chores at home, which he does, but usually with reluctance.

He has a sister 3 years younger and another sister 6 years younger who has Down's syndrome.

He spends virtually every minute at home unless he is at school or at his other activities. He pesters his sister, makes cookies, works on his model railroad and reads about computers. He is an avid computer/gadget tinkerer. His main interest is model railroading and bicycling, although he really doesn't do any cycling except to the bus stop to go to school.

My husband is away on business at times and doesn't spend a whole lot of time with our son, but does try.

My son used to have friends. A little over two years ago we returned from three years overseas. We returned to the same house and school, but he no longer fit in with his friends on our old block. In fact, all the boys -- around four -- turned against him and made living very tough for him. The person he always considered his best friend for years even turned on him.

I tried to get to the bottom of this discreetly but still am at a loss to discover what happened. My son said when we returned, "They've been here doing the same thing and I've been to so many places." But he wanted to be friends again with those boys.

We have now moved a few blocks away but have stayed basically in the same area of school, church, Scouts, etc. I thought at some point my son would make friends at his new school, but that hasn't happened. Neither has he kept what few acquaintances he had. He is very reticent and doesn't talk much about his feelings or problems.

I just feel it is not good or normal for him to spend so much time at home, doing no sports and having no friends. I'm afraid he's going to grow up warped and alone. He's not a bad kid. I rather enjoy being with him, or did until the last two years.

A. You're right. If all were going well with the boy, he would make other friends. Although some people enjoy more privacy than others, no one chooses to be as isolated as he is and certainly not a child who once was a friendly sort.

You need to find the cause so you can help him deal with the effects.

Moving is tough on a child, especially a move from one culture to another and especially in the middle years. It makes him feel different, and just at a time when conformity counts.

At around 7, a child's individuality and personality begin to get more and more defined. This makes him so uncomfortable, he tries to look and act just like his friends -- a pattern that lasts all through his middle years. It's easy to see that your son would have felt different when he came back from overseas, but the problem should be gone by now.

There are other possibilities to consider.

When he left home, his retarded sister was only 1; when he returned, she was around 4 and to his mind, she must have seemed very conspicuous.

This could have triggered a small, awful incident between your son and his friends, not because children are as cruel as they're painted, but because they're so candid. This is understandable. Their social skills are small compared to their parents -- and yet many adults have a hard time talking gracefully to a friend about their child's retardation.

Even if his old friends said nothing, your son may have been afraid that they would, or been so embarrassed that he turned himself into a shut-in.

Let's not pretend: A handicapped child can mean, to some degree, a handicapped family. It's also true that the family may be more sensitive, more appreciative, for they know how big a small accomplishment can be. But the scale can be balanced, and sometimes more than balanced, by the extra stress. There is extra worry, extra expense, extra vigilance.

The marriage may be under more stress than most and the other children in the family, although they love the handicapped child, may feel embarrassed and angry, which makes them feel guilty. A few sessions with a psychotherapist for your son, or maybe for the whole family, would let him know he wasn't alone. A Difference in the Family by Helen Featherstone (Penguin, $4.95) also reminds you that you're not alone.

Even if the problem stems from something outside the house, it may take a professional to make him seek friends again, but don't expect miracles. A 12-year-old will pester his sister, drag with his chores and do less than he might in school (and he'll keep right on acting this way for the next 6 years).

You also can help your child in more concrete ways. The born tinkerer needs some interesting chores -- to fix the doorbell, replace the washers, rewire a lamp. It's good to feel needed.

And steer him toward a group where he can meet his own kind. At 12, he's old enough to go further afield for his friends, which he may find at a model railroad club, a Saturday computer class or in the children's branch of a computer club. Every major brand seems to have one in or near most of the big cities -- including yours.