Most of us think of latchkey children as lonely waifs who prowl the streets after school because their mothers are out driving a bus, practicing law or selling real estate for a living.

What we don't realize is that latchkey children are a hot consumer market - so hot, in fact, that clever retailers are pitching their ads to small shoppers with money in their pockets.This startling revelation comes to us from Joan King, a perceptive advertising executive who runs J.K. Communications in Glen Ellyn, Ill., just west of Chicago.

"Who is this advertiser's dream? Today's latchkey kids. That's who," writes Ms. King in a bimonthly newsletter published by the Retail Advertising Conference in Chicago. "They're buying much more than clothes, bubble gum and electronics gadgets.

"You'll see some of them in the convenience store after school buying - not soda pop - but Perrier. You'll see them doing the family grocery shopping. They do much of the household cooking, laundry and cleaning and they have a lot to say about which microwave they'd prefer and which vacuum sweeper they can handle.

"They have a major influence in buying television sets, computers, washing machines - even cars."

You may wonder how much buying power children really do have. Not much, you say. That's where you're wrong. An organization called Teen-Age Research Unlimited in Lake Forest, Ill., contends that children 12 to 19 are spending more than $31 billion of their own money and more than $47 billion in family money this year.

Peter Zollo, executive vice president of Teen-Age Research, says his figures are based on questionnaires filled out by a national sample of 2,000 teen-agers. "A lot of these are latchkey kids," he says. "Most of their mothers are working.

Selling to a 15-year-old is not the same as selling to his or her 45-year-old mother. The Norman Rockwell approach - lots of old-time schmaltz - won't do the trick.

"Kids today don't care if cookies taste like the ones their grandmother supposedly baked," says Ruedi Roth, a Chicago packaging expert. "The latchkey kids don't know or care what was good years ago. They want with-it, now products."

Bright colors are in vogue. So are short, flashy names.

The notion that latchkey children are a market, not a social problem, is a bit jarring. We're talking here about kids who may be as young as 9, 10 and 11. Are they safe? Are they lost? Are they setting fire to the house?

"I don't think there is a working parent in America who isn't terrorized by the latchkey-children problem," says Rep. Patricia Schroeder, D-Colo., who campaigns among her mostly male colleagues for parental leave and child care legislation.

But if children are doing the shopping that mom used to do, the advertising they see is like school out of school. They'll soak up the bad stuff along with the good.

"I worry about violence in ads. I have a real problem with kids growing up too fast - sexy clothes for 12-year-olds, that kind of thing," says Joan King.

My own suggestion is that we use advertising to teach children to speak English.