Q. In your Dec. 20 column a woman wrote you about her 3-year-old who had suddenly turned into a monster.

You offered a lot of suggestions -- diet, nightmares, Halloween, pinworms -- but you overlooked one large one. The child may simply be too young for nursery school.

There are no more tearful farewells perhaps because he has learned that they don't work. He may say his mother is yucky because he thinks she is yucky to leave him. He was not quite 3 when she did. Just as not all children can handle all foods, not all children can handle strange people and surroundings.

The conventional wisdom now seems to say that even a small baby should be able to take being left with anyone, any place. But suggest that this lady read any of John Bowlby's books and think about it.

If the child doesn't start school until he is 4 or even 5, it doesn't really hurt his chances to get into Harvard.

A. There are pitfalls in being a self-proclaimed expert on parenthood when parenthood is your only credential.

Like never having heard of Dr. John Bowlby.

After doing some serious checking, however, we have a hard time applying the results of his "separation anxiety" studies on children in institutions to children in nursery school nine hours a week.

When a parent abandons a child suddenly, with or without warning -- because of death, divorce or hospitalization -- there is sure to be trouble. However, the mother who kisses her child goodbye on the sidewalk and is there to met him three hours later is simply teaching him what everyone has to learn: that it is safe for a parent or a child to go away. The child who hasn't had the practice of these temporary situations is the one who falls apart when he has to spend six hours a day in first grade.

We also doubt that attendance at nursery school helps a child get into Harvard, or Northern Virginia Community College either, nor do we think this mother enrolled her son because it would look good on his resume in 1994.

Like her, we think nursery school genrally is pretty good for most children (not all, just almost all). And we agree with you: The starting age depends on the child, although a Three is usually ready, particularly after a few weeks when the people and the surroundings aren't strange any more.

You can tell if a child isn't mature enough for nursery school because he cries when he is there -- not afterward -- and when he gets home he acts babyish, begging to be picked up, and maybe rocked and cuddled. He even may beg for a bottle or need diapers again and he may follow his mother from room to room.

But this is not the sort of child this mother wrote about. Instead two months after school began he not only started acting like "a monster," but he started getting scared of them too -- and just a few days after Halloween. We still think there may be a direct connection.

As Dr. Stanley Greenspan, the child psychiatrist who directs the Mental Health Study Center at the National Institute for Mental Health, says, "First you take an inventory of everything that has changed for the child -- at home, at school, with his parents and his peers -- and then figure out the changes in him. Fears seem a likely hypothesis. As a child gets to age Three, he can take an actual experience -- like a monster he saw on Halloween -- combine it with something else he saw and get a whole new fear. This is because the higher level of memory has gotten to work. Now he both retains memories and amplifies them."

To us, the good times -- and the psychological values -- that this child is getting from nursery school should far outweigh any mild uneasiness he has about being away from his mom three mornings a week.

Not to play a game of "gotcha," but as psychologist Lawrence Kohlerg says, you can't have moral development without social interaction.

From a reader: I'd like to comment on your Parents' Almanac of Thursday, Jan. 10. It left me with such a sad feeling for the woman who wrote you. Her children were only 5 and 8 when she returned to work and with all the pressures she feels unable to cope with her life.

She says the family could afford to have her stay home (if they economize more), but she's afraid she might feel "worthless" -- the implication being that worth equals salary.

If she doesn't look down on the person who takes care of her children, why should she look down on herself?

It sounds as though she is trying to manage her life by the standards of others. She must find what works for her and ignore these pressures.

Many women feel more alive and vital when they work and therefore they should work. But this woman doesn't feel like that.

I wish we could picture the more positive side of homemaking. Many of us at home make no excuses -- we enjoy our families and home and husbands. We not only cope but thrive and life is rich and rewarding. My husband has peace of mind and knows the home is not only there but well-run, organized and happy. We agreed when we married, that he would make the living and I would make the living worthwhile.

I think your answer was unusally good. Part-time work is an obvious solution but she must learn not to feel guilty about wanting to be home with the children. Hopefully, by following your advice, the sad woman will search her heart to find a better way to live.