It's 3:15. The kids burst in the door, toss their schoolbooks and get down to business.

"I'll trade you a pizza for a chocolate or a bubble gum. That's a good deal," I overhear.

What's this? An after-school snack co-op? A pint-size catering caper? No. It's the hottest collecting/swapping phenomenon going among little people. It's the craze of smelly stickers, a.k.a. stinky stickers, a.k.a. scratch'n'sniff.

From mint chocolate-chip ice- cream cones to skunks, from Lifesavers to cowboy boots, the little stickers picture almost anything thing with a smell. You scratch the surface with your fingernail and sniff a scent often remarkably like the real thing. Many of the stickers are smiling edibles mouthing catchy phrases: A caramel apple grins "Stick to it"; a dancing pickle sings "Dill-ightful."

Kids buy them by the dozens, file them in photo albums or slick, commercial sticker books, and then trade, trade, trade. The smell of the stickers is just one clue to their appeal but a major factor in their Relative Trade Value on the open market. The kids are experts on an intricate value hierarchy.

"Is this chocolate one good?" I ask the family sticker authority. (Smells yummy, almost like Swiss chocolate to me.)

"Naaw, Mom, chocolate's not very rare at all."

"Rare" is the key term to define all sticker transactions. A sticker is rare if it's hard to find and a rare sticker is a hot trade item. One kid was heard negotiating, "This one's on the tip of rare." And you're getting "gypped off" if you don't know better than to trade Big Popcorn for Big Orange.

Unofficial reports confirm that the sticker craze has struck in Florida, Kentucky, Pennsylvania, New York -- even Bayonne, New Jersey, where our cousins in an Orthodox yeshiva say the bug has bit big.

Where's all this leading? One principal's plea gives a clue: "Help! Help! The smelly stickers have become a problem! It started as a rather innocuous activity by the students, but we find it is interfering with classroom instruction. Please do not allow your child to bring them to school," reads Mrs. Joan Peck's memorandum at Wood Acres Elementary in Bethesda. The response? After-school smelly- sticker swap clubs, of course.

Stickers become a state of mind with kids. On a recent nature walk at Great Falls, Maryland, the park guide showed the class a Spice Bush, whose leaves emit a pungent smell when crushed. "Wow, natural scratch'n'sniff!" chorused the students.

You can find stickers and sticker books in every gift, variety or department store with an interest in making money. Smelly stickers aren't cheap: A packet of 24 ranges from one to two dollars; individual stickers go for 10 to 25 cents each. With many collections ranging in the hundreds, that's a pile of quarters.

There are, however, beneficial side effects to the negative cash flow of this fad. Increased child labor is one. Our eight-year-old sticker enthusiast has become the family Golden Boy:

"Can I do the dishes, Mom? How about vacuuming the rugs?" he solicits. No lucrative task is too demeaning if it means maintaining his sticker habit.

As I dole out the dollars, I tell myself that collecting is character-building; that working, saving and buying is the American Way. Better sniffing stickers than glue. Still, I wonder, who's getting rich off all those allowance dollars, and why didn't I think of it first?

Time was that the value of kids' collectibles was obvious to all. You could trade a Mickey Mantle for a Yankee team card, a cat's eye shooter for three blue marbles. Today's bartering is more esoteric:

"Mom! I got 'Dry martini' today. It's soooo rare!"

"Really? That's great."

"Mom -- what's a dry martini?"

"What's it smell like?"

Scratch. Sniff. "Kinda like peppery soap."

Yep. That's a dry martini, all right. What will they think of next?