Longer skirts and minimal skin were trends at from left, Louis Vuitton, Prada and Fendi. Photos: Antonio de Moraes Barros Filho, WireImage.com; Christophe Simon, AFP/Getty Images

Now, pay attention, class. You will be tested. If a runway model wears her skirt well past her knee, covers up practically all visible skin on top, but manages to still cause a stir with her stern, yet sophisticated style, what fall trend is she following?

Let's see a show of hands. The correct answer: Dressing like a sassy school marm.

"The long skirt trend is re-emerging because designers realized that not all women can or should dress like Beyoncé in micro-mini, shimmering tight dresses," George Kotsiopoulos, co-host of E!'s "Fashion Police with Joan Rivers" tells StyleList. "This trend is classic and will never go out of style, as it's very flattering on so many women. Oscar de la Renta, for example, does this silhouette every season with great success."

It could be a sign, Nordstrom Fashion Director Gregg Andrews says, that overt sexiness on the runway has hit its limit.

"It's gone about as bare as it could have," he tells StyleList. "The natural cycle of fashion is to cycle back around the other direction. What we end up with is a more pure form of femininity. Last fall it was all about a very strong, very aggressive woman. This fall, it was more about a strongly competent woman who didn't really need to fight. She'd already arrived."

To help you earn an A+ in making the school marm/ladylike trend work for you, we asked experts Kotsiopoulos and Andrews for a lesson in wearing the look. Consider this your style cheat sheet.

How do you keep a long skirt looking fab, not frumpy?
  • "A long, full skirt can be dowdy on women of a certain age unless you sex it up and flaunt your best assets," Kotsiopoulos says. "At Louis Vuitton, it was all about cleavage, which offset the frumpiness of the skirts worn with kitten heels. The retro look of a full skirt and kitten heel is fresh on a young girl, but will mature a woman in her 40s beyond her years."
Some of the runway looks were so severe. Can I pull that off at home?
  • "Women don't need to mimic the exact look they see on the runway," Andrews says. "The compass says hemlines are getting longer -- it doesn't mean you have to wear a skirt below your calf, it doesn't mean you have to wear a skirt down to your ankles. Wear a longer hemline that works for your proportion and, for most women, a longer, wearable hemline is going to hit right below the kneecap."
Help! I'm petitie. Won't a long skirt swallow me whole?
  • "A full skirt on a petite figure can be overwhelming if it's not the right length," Kotsiopoulos says. "If you're not shopping in the petite section, it's important to remember designers' fit models are 5'10", so you need to adjust length accordingly. The length on a fuller skirt should hit about mid-calf."
What about us curvy girls? Do these styles still work?
  • "Fuller skirts are a good option for full-figured ladies if they have a defined waistline," Kotsiopoulos says. "Otherwise, it's best to stick to more streamlined silhouettes or a skirt that hugs the waist but flares out at the hip. These styles have structure built into the garments to either enhance or create curves, making them ideal for many body types."
  • Andrews says it's all about fit and proportion and how the skirt fits through the hips and the seat. "For a woman with curves, a longer length skirt can definitely flatter her, but she needs to make sure that it's not too tight and she also needs to make sure it's not too full, where it starts adding the illusion of pounds," he says, agreeing that a curvy woman needs to define her waist. "That helps define the bust line, that helps define the hip line. Having curves is great. I think 'Mad Men' has really helped bring curves back into fashion."
When it comes to color, what should I look for?
  • "Full skirt looks in bright colors can turn prom very quickly, which is great if you're a young thing, but silly on an older woman who should stick to the minimalist fall tones of black, navy, camel and gray," Kotsiopoulos says.
  • Andrews agrees, saying grays, blacks, deep blues and plums look sophisticated. "There's more of a minimalist aesthetic to it," he says. "It's not really as girly or as prissy as we've seen it in the past. It's very clean. There's a strength to it without seeming overly precious."
OK, I've got the skirt, now, what do I wear on top?
  • "It's important to be streamlined on top and cinched in at the waist in order to show some shape, since the full skirt hides most of a woman's body," Kotsiopoulos says. "Here's a great opportunity to show lots of skin on top, as my rule for classy ladies is choose two of these three: chest, arms or legs. Baring all can be tacky, but two is just the right amount of skin."
  • Andrews says you definitely need something that tucks in or defines your waist. "It can be a simple shell, it can be a soft tailored blouse," he says.
And what about accessories?
  • "Sky high heels modernize the proportion and add some va-va-voom to an otherwise dowdy look," Kotsiopoulos says. "Retro accessories like pearls and gloves should be kept to a minimum to avoid looking like you're on the set of 'Mad Men.'"
  • "Animal prints are a great investment, because they never really go out of style," says Andrews. "Think about an animal print belt or maybe a blouse. But one piece of animal print at a time, please."
  • Andrews also says this is a good opportunity to play with hosiery, especially if emphasizing your calves and ankles isn't something you're dying to do. "You start matching your hosiery to your hemline to your shoe," he says. "If you do it right with your shoes and your hosiery, you can have this great long, unbroken line from the waist down to the tip of the toe."

Looking to increase your learning curve on other fall trends? Here's how to dress like a minimalist.

And click here for 5 ways to rock old lady style.