Not so long ago, the arrival of August triggered hordes of families rushing store to store to stock up on just the right back-to-school stuff.

The uniform varied from year to year, but it was usually predictable. Trendy sweater coats, colored denim washes, chunky high-heeled boots, graphic T-shirts and status sneakers came and went.

But today so many ideas are floating through the teen market, it’s impossible to narrow the field to a specific look.

“People talk about preppy, urban or surf. It’s not about any of those. It’s about all of those,” says Marshall Cohen of NPD, a sales tracking company. “They mix and match everything.”

Today’s teens are more confident about making choices and less concerned with following a leader. They want to assemble their old and new clothes in a way that reflects their own style and sets them apart.

Like their parents, they have become savvy shoppers. They tend to go to discount and conventional retailers and vintage stores to get the best bargains for their dollar.

Technology is a big part of teens’ wish lists, and it has eroded the clothing budget. “Teens are spending money on (cell) ring tones and text messages,” says Jillian Hertzman, spokeswoman for Youth Intelligence, a New York-based market research company.

Experts tell us brand names have waned in importance and high school students are expected to look a bit more polished. It’s a subtle change, but pants are coming up a tad on the waist, leaving less flesh flashing.

Some trend-conscious girls may want to include a short close-fitting blazer in their wardrobe. Guys are even appropriating skinny ties and brim hats from long-ago eras. “Grandpa” hats, they are called, Hertzman says.

As trends go, the preppy look takes center stage for both genders. But what makes it especially cool is mixing the prep with other styles. A guy wears a preppy sweater vest over a rock T-shirt, or a rugby shirt or button-down oxford with frayed, worn-looking denim. He also adds suspenders and a blazer to baggy cargo pants. Ditto for argyles.

Girls are putting plaid miniskirts with flip-flops and T’s. They pair argyles with denim pleated minis and short tweed jackets with jeans. They’re pulling on girly-girl tops with ruffles, lace, pearls and broaches but then diluting the femininity with jeans that look as if they’ve been around forever.

Layering in general is on the to-do list. Guys put short-sleeved sweaters over long-sleeves. Girls put vintage-looking embroidered sweaters over T-shirts and get sassy with ponchos topping tank tops. Ponchos are expected to be popular.

What’s hot for girls

Jeans that appear well worn and a bit frayed; girly-girl tops with feminine touches, often with frayed jeans; pearls; ponchos; shirts with Western touches; cowboy jeans; pleated, short-flounced skirts in denim or plaid; layered T-shirts in bright colors and layered everything else; and screened graphic T-shirts.

Also, grommet belts; colorful tights; argyle sweaters; ribbed polo shirts; retro embroidered cardigans; dark denim jeans for a more polished look; blazers; flip-flops; boots with pointed toes; and slightly higher-waisted jeans.

What’s hot for guys

Well-worn authentic looking jeans; cargo pants, sometimes in fleece; stylized graphic T-shirts with images of everything from rock bands and bikers to animals; sweater vests for prepsters mixed with grunge; rugby shirts; skinny ties; suspenders; boat shoes or Top-Siders, slightly polished; polo shirts; Grandpa hats; argyle sweaters; blazers; suede boots lined with fleece; and iPods worn on belts.