Q. "I am encountering problems with my 2 1/2-year-old daughter that both puzzle and concern me.

"For the past few weeks there has been a considerable change in her behavior. When she began nursery school in March, she was eager to attend. In fact, she ran in and immediately began to play. Now she refuses to sleep in her room and will not go to the bathroom by herself. She cries and becomes very upset when left at school and is becoming timid and afraid of everything.

"Is it normal for an outgoing, pleasant child to change so suddenly? Is this unusual behavior, just a "stage" or should I take her to the doctor?"

A. Any time a child's behavior changes drastically -- at any age -- something is the matter. And when it changes just after she starts nursery school, there is almost surely a connection.

Nursery school can be so good for a child, but only if the school itself is reasonably good and if it suits the needs of your own child.

There's only one way you're going to find out: You have to go to nursery school yourself. Tell the director that you'd like to observe and arrange a date soon. Get there early and stay until it's over. No matter how much you want to read the children a story or feel you should mop up the juice, remain an observer so you won't change the atmosphere too much.

Watch the children as they come in. Do they seem happy to get there? Do they play fairly well with each other? Is anyone allowed to be a bully? Is there a lot of crying?

Does the teacher stay in the background, or does she need to be the center of attention? Does she order the children about a lot? Does she realize that this is the time children are supposed to get ready to read -- by learning how to move their muscles and track their eyes -- rather than learn their ABC's.

Is there a sense of order beneath the chaos, a feeling that everyone knows what's going to happen next and is fairly ready for it?

Ideally, the school should have a warm, accepting teacher, some aides who work well with her and keep the program flowing; a good deal of exercise, walks and adventures; a chance to rest; crackers and fruit or pure but diluted fruit juice; some plants to tend and food to cook; hammers, paints and play dough; puzzles and put-together toys; good books and records; a chance to dig in sand and play in water, even indoors in winter; balls of assorted sizes; tricycles, Big Wheels and a wagon.

Even a school that's missing half of these ingredients may charm a child, if she likes her new friends very much, or if the teacher is extra patient and caring, or if the school has a special asset, like its field-trip program or fine outdoor playspace.

The problem, of course, may be only with your child, so you want to study that too. Some children simply aren't ready for nursery school as early as others, and 2 1/2 is mighty early, especially if she goes every day. When a child is tired or under stress, she is sure to start acting younger.

It even could be a new stage, as you suggest, but a child would be rowdier, not more afraid.

It could also be a reaction to something she eats or smells or touches as school, like a disinfectant or the guinea pig, or she could have picked up an infection. Chart her behavior, record her temperature for a few days and then let the doctor examine her. Be sure to tell the pediatrician any symptoms you've noticed, even if they seem irrelevant.

If you can't find anything the matter, or if the situation at the school can't be changed, then your daughter should be withdrawn. She can try nursery school again when she's had plenty of extra loving at home to become her old self again. Even when you think she's ready, you should only let her go if she is eager for it and you've seen her play there happily for several mornings. You have given her such a good start, you don't want a nursery school -- or any school -- to jeopardize it.

Q. "Our 9-month-old son shows no inclination to crawl, although he does love to stand and take a few steps while holding on to our hands. We thought very little of this until friends told us that there may be a correlation between non-crawling and later reading problems.

"We are wondering if we should start a crash course to teach him how to crawl."

A. Your little boy would probably have a wonderful time if you scrambled around on the floor with him, but don't expect it to make him read better.

Florence Hesser, director of the Reading Center at George Washington University, and Sally L. Smith, who runs the Kingsbury Lab School for learning-disabled children, both say they've seen too many kids who crawled before they walked -- and too many good readers who didn't -- to believe there is any real connection.

But by all means get down on your hands and knees and crawl alongside your little boy. He's sure to be amused.