Q. My 6-year-old son recently told me that he and a friend frequently play a game where they take off their clothes and then lie down, one on top of the other. They call it "doing sex." He says this has only happened at the other child's home during afternoon playdates.

My son said they learned it from a third boy in their kindergarten class, who made him play the game while they were alone together at a birthday party.

Was my son the victim of abuse? Could that boy be the victim of abuse himself?

My son won't be visiting these boys again. Their parents simply arrange these playdates, then let the nannies supervise the boys (or not).

Are sex games normal at this age? Is my son gay? Should I tell the other parents?

The idea of someone touching my kid against his will upsets me terribly and so does the idea of homosexuality. I thought I was fairly progressive, but apparently I'm not.

A. Responsible parents are never as progressive as they think they are, nor should they be. Children need their parents to rear them conservatively, watch them carefully and step in at the first sign of trouble. And that's what you must do.

Stop those playdates, since neither the nannies nor the parents are good supervisors, and keep your son away from any friend who tries to force him to do anything.

Also be frank with the parents. And talk to the school counselor if you think one or both boys has trouble at home. Don't accuse them of sexual abuse, however -- they're too young for that -- and don't think their games are a sign of homosexuality. They're not. Those three children were just doing what comes naturally, in their own rather original way.

According to Family Almanac mail, masturbation is mighty popular with both sexes between 2 and 6.

All boys and girls instinctively find ways to enjoy sex, not because they're trying to achieve an orgasm, which they can't, but because it feels so good. It's only around 7, when modesty sets in, that children try to hide their urges even from themselves. The association of sex and pleasure doesn't fade away; the play just gets more discreet and usually less frequent.

It's your job to accept your child's interest in sex without shaming him and without letting him get sexualized too soon.

When a child plays with himself in public -- even if he's just in the living room with you -- tell him that it's all right to do that, but he must do it in private, which discourages this activity nicely since young children don't like to be alone very long.

When you hear children play "Show me," tell them to stop because the penis and the vagina are not toys and when two or more children are in a room alone, make them keep the door open. The rules you will insist upon at 16 are just as essential at 6.

Questions may be sent to margukelly@aol.com or to Box 15310, Washington, D.C. 20003.