one who is active, cocky, eager and sociable -- I am trying to make sure he develops a moral code. For the most part he knows right from wrong. And yet I'm not sure he has learned that all people are equally human.

In his kindergarten class is a child who is very obese. And to my son and his friends, she is referred to as "the fat girl." He, along with others, takes pleasure in ridiculing and tormenting her. From him I have learned that they steal her shoes, poke her and stand behind her pulling her hairs one by one.

The teacher rightly punishes them routinely by having them all sit or stand aside. My son thinks this is terribly unjust. He seems to believe there is nothing mean or low or wrong with abusing this child. I can't help feeling that he looks on this child more as a toy than a classmate.

His father and I have talked with him about it. We've explained that it isn't her fault that she's the way she is any more than it's his fault that he isn't. Nothing seems to register, even telling him that the more he picks on her, the more time he's going to spend in the corner. It's like talking to a wall.

He's not generally such an insensitive lout. I've seen him defend friends from the taunts of others. Nor is he so asocial that he ridicules someone who looks different from him.

A: Six-year-olds don't walk in any shoes other than their own. They are still egocentric creatures and most of them will be for another year or so.

It would be easier for him to think of himself as Superman than as a fat girl, and this is because Superman, although imaginary, is his friend. At this age, a friend is really an extension of himself.

That's why he defends his buddy, but since the overweight child isn't a part of his life he feels he can torment her.

Moreover, the team spirit has made the ridicule more likely. Each child encourages the others to say and do more outrageous things, just by being there.

All of this may explain your son's behavior but it doesn't excuse it -- and neither can you.

Endless reasoning with him won't help since he hasn't reached the age of reason, nor will second punishments, but he will take notice if you're obviously angry; if you say you just won't put up with his meanness; if you compliment him when he doesn't take part, and if you tell him, with great solemnity, that such behavior "is not in the family tradition." Children like traditions and they like to aspire.

Even if you did none of those things, any child who's reared by loving parents will outgrow his churlish ways, but in the meantime, a little girl suffers -- and no matter how much she weighs, she's still a little girl. It's bad enough to be embarrassed by her classmates, but when the teacher calls attention to their behavior by punishing them publicly, she is victimized not once but twice.

You have to wonder how the situation got so bad at school. Something's wrong when punishments are "routine," or when they have no effect. The only good discipline is the kind that works and like medicine, the kind that works best is preventive. The teacher should tell the class that she won't tolerate any more mean behavior between any children -- without mentioning the little girl, of course -- announcing this on a day when there is no trouble. She also should warn the young terrorists individually, keep them apart as much as possible, look very cross whenever there is the slightest infraction and admonish them privately if there is a violation.

Above all, the teacher should congratulate the ringleader of the week for even the slightest improvement. Children would rather be noticed for being good than for being bad.

It also will be harder for them to mock the heavy child if the teacher gives her more time, praises her whenever she uses her talents and helps her make more friends in the class. It will be hard for one mob to take on another, even if it's much smaller. To bring about these changes, you'll have to see the teacher and tell her how much this behavior bothers you and how much it undercuts the values you try to teach at home.

And if she doesn't make changes -- or doesn't see how she can -- you'll want to ask the principal to show her how to handle classroom problems better.

Maybe none of your efforts will help at school, but your seriousness will show your child how much the problem upsets you. This will make him obey better, not because the girl matters to him, but because you do.