Guess what else is new for high school students this fall, aside from mottled blue jeans, Esprit mini-skirts and mock turtlenecks?

How about an answering machine designed for a school locker?

The machines come with three ultrasound activators to give to classmates. Activator-equipped friends then mumble 20-second messages through the locker vents.

"It is the stupidest thing I've ever seen in my life," said Angela Kobe, a senior at Fairfax High School.

Sean Anderson, another Fairfax senior, disagreed. "I've seen it -- it's bad. I'd do it."

"Oh my God. Oh, that sounds great," said Glynn Bates, principal of West Springfield High School.

"So, now we're going to see all the kids talking into the face of the lockers?" asked Ray Volrath, principal of Thomas Jefferson High School for Science and Technology. "Gosh, that's all we need."

The answering machines are the creation of a California company, Worlds of Wonder.

"Worlds of Wonder Inc. is betting that America's high school and college students are ripe for a change," says the company's promotion package, "and plans to invigorate the market with an invasion of fashionable, upscale and useful school accessories."

The answering machines come in one color -- a subdued gray -- because, as Worlds of Wonder's Bill Grubb said: "This is the year of earth tones in terms of most of their wardrobe."

The first machines were shipped five weeks ago from California, and are just now reaching Washington metropolitan store shelves.

Jimmy Jenkins is manager of Fairfax City's Toys R Us store. "We've had calls for them," he said. "The call I took was from an adult. They said they had been calling around, and no one had it yet."

In Shirlington, a shipment of 50 machines arrived yesterday at the Best Products store.

"It's definitely going to be a big thing," said assistant store manager Teresa Sulenos. "As soon as I saw it, I said, 'No doubt about it.' "

Allan Kalish, research director at Seventeen Magazine, said his teen-age sons probably wouldn't be interested. But a Seventeen survey three years ago found that more than 60 percent of teen-age girls would be interested in a portable phone message relay device.

The machine is battery operated, and can be hung on locker hooks, or attached to the locker wall with Velcro. A flickering light indicates that a message has been left. There's a special earphone jack that provides for private student screening of messages -- as many as 180 at a time.

Students can use stereo headphones, if they'd rather.

"We do not allow students to bring in Walkmen and go around wired up, so that would be the only obstacle," said George Kiem, principal of Chantilly High School. "I wouldn't want students wandering the halls with headphones on, listening to messages."

Peter Zollo is vice president of Teenage Research Unlimited. His Illinois-based firm has tracked habits of students aged 12 to 19 for years. He knows, for example, that 56.8 percent of teen-agers own their own telephone, and that one-quarter of teen-age males bought hair styling mousse within the last three months.

"This is definitely a different breed of teen than in the '60s or '70s, or even in the early '80s," Zollo said. "They're so style-conscious, fashion-conscious and money-oriented."

Teen-agers are also partial to products that are outrageous and high-technology and involve their friends, he added.

"That's why when people ask me if marketers are changing their tunes in going after today's teens, I usually cite the locker answering machine as something that is perfect -- right on for today's teen," Zollo said.

The machine is designed to retail for between $40 and $50.

Said Kalish: "Forty to fifty dollars -- they spend that on jeans."

The average teen in the United States spends $21.43 a week of earned and allowance money, according to Teenage Research Unlimited. Total, this year, the nation's 33 million teens are expected to spend $34.4 billion of their own money.

Similar research accounts for Worlds of Wonder's confidence in the locker answering machine.

"Over 30 million homes in the U.S. have telephone answering machines, and we've found out that where there are teen-agers, they are the heaviest users of a telephone answering machine," said Grubb, executive vice president and general manager of the firm's school accessories division.

"Kids just hate to miss a message."