Q. I'm 15, my sister is 13 and we have a younger brother who is 9.

He often teases us by trying to look under our dresses. Our parents try to discipline him and he will stop for a while but lately it's gotten much worse. Yesterday in the mall he snuck up behind me and actually lifted my mini-skirt in front of several people.

How can we deal with this annoying and embarrassing problem?A. When you mix the middle years with adolescence, it can be rather explosive. Anyone who has a little brother is almost sure to be teased, and anyone who's 15 or 13 is almost sure to be angry about it.

A child is more likely to tease at 9 than he will at many other ages. Whenever he is bored or lonely or feeling full of mischief, you can expect him to tease someone. And what better target than a big sister -- or two?

To a 9-year-old boy, skirt-lifting is both funny and fun. This is because he's an exuberant little rascal and a bit of a smart aleck and he's at that way-station between bathroom jokes, which delight an 8-year-old, and dirty jokes -- the trademark of the 11-year-old.

This doesn't mean you have to put up with this or any teasing that invades your privacy.

Children are in charge of their own bodies. No one has the right to touch them or make fun of them or try to see what's covered up, not even a little brother, and not even in jest.

You and your sister are understandably embarrassed and annoyed because you're both especially conscious of your figures and your appearance now but in your anger you've created a circular sort of problem. The more you react to a particular kind of teasing, the more your brother is going to try it.

So what should you do about it?

It will be your actions that put a stop to his. As long as you get mad, throw scenes and run to your parents, he's getting what he wants: your goat. Instead, he deserves the same detached treatment you'd give anyone who made an improper comment or a sexual advance.

When he turns up your skirt, brush it down as if it were ruffled by the wind and look into the middle distance as if he wasn't there at all. He'll just look silly if you don't react -- and little boys don't like to look silly. Conversely, you don't want to look grim, with a firm chin and a set mouth, nor do you want to make eye contact, because he'll see your anger and know that he has won the exchange.

Don't expect this new approach to stop him in the beginning. In fact, he may try more skirt lifts than ever when you first start ignoring him. If he does, you'll just have to tease him back. That's when you say, low and clear, "I know who your girlfriend is" -- and then drop the subject. It's amazing how quickly a little teasing from a big sister can deflate a 9-year-old male.

This is not, however, the basic reason to do it. You have to make your brother realize that it's unkind to make fun of people, particularly in a sexual or personal way and you have to explain this with love and with care.

Do it in a quiet and friendly talk with him, which you initiate, but don't be angry or accusatory. Instead, tell him that you're sorry if you embarrassed him but that he has to understand that you and your sister feel just as embarrassed when he tries to look under your skirts.

He'll probably still keep teasing you -- in fact, he surely will -- but he'll do it in other, more acceptable ways.

You'll have to accept this other teasing in the spirit in which it's made -- a plea for more attention from the two people who mean almost as much to him as his parents.

This is what is probably so hard for you to believe. You and your sister are so important to your little brother that he's eager for any attention you give him. If you only notice him when he misbehaves, he'll only have one alternative. He'll have to misbehave even more. The child who feels shut out is the one who needs to tease the most.

You can make your brother feel more welcome with an invitation to a movie, just the two of you, or your sister can ask him to help her make holiday cookies. When he feels like part of the club, he'll treat its members better.

He not only needs your attention but your understanding and patience. This may not sound too appealing, but in time these kindnesses will help him get over his foolishness.

You won't regret making the effort. Your little brother, as pesky as he is, will be your lifelong friend but you have to work on it now. If you wait until he's old enough to be interesting, you may find he isn't so interested in you any more.