New York Fashion Week came to a close Thursday with Ralph Lauren exploring sexy schoolgirl chic and Calvin Klein offering up a study in geometry for next spring.

Marc Jacobs was to close the massive final day of fashion frenzy in the Big Apple, before the spring-summer 2014 style cavalcade moves over to London, Milan and Paris.

Lauren added his own twist to one of the major trends of the season -- the classic combination of black and white -- sending out a bevy of saucy schoolgirls in short skirts and dresses with a 1960s flair.

Klein's new collection was a study in geometry with loose, box-cut jackets and tops -- another key theme of the week -- and skirts given a square shape with a side hem.

There was a bit of something for everyone at fashion week: masculinity was mashed with romanticism, while elegant looks took on a sporty feel. Not only will plastic be in fashion next spring, but it can be mixed with lace or tweed as well.

White is fine all the time. As for hemlines, dresses can be short and flirty, knee-length or fall 1950s style to the calf.

"There are no more rules about length," Nicole Fischelis, fashion director for Macy's, told AFP.

"Nearly all the collections opened or closed with white, and it's not boring -- it has transparency, geometric effects, layering, 3D embroidery," she said.

She said a lot of the looks unveiled reflected "a new minimalism".

The must-have item for next spring for women is a shirt-dress.

"His shirt has become ours", Fischelis noted.

Another theme seen across practically all shows is that fashionistas can finally breathe -- gauzy transparency was everywhere.

Dresses were loose and square and -- as seen at Calvin Klein -- drop-waisted. Skirts were also fluid and full, and tops and trousers oversized and slouchy.

With actress Jessica Alba in the front row of a white runway lined by black seats in downtown Manhattan, Lauren opened with a short black dress with a white collar paired with knee socks.

His next dress added some leather and a black tie to the saucy schoolgirl look. Striped blazers, jaunty caps and a studious pair of glasses on one model rounded off the look.

Fashion week has seen plenty of geometric prints, from stripes and polka dots to fashion queen Carolina Herrera's use of kinetic art inspiration and layering to create vision-bending multidimensional motifs.

The 73-year-old Lauren used stripes and blocks, but also put a triangular print on a coat which he paired with a shiny skirt, crisp white shirt and floral print black-and-white tie.

Shiny sateen, neoprene, and scuba-inspired material have been used by everyone from Peter Som to Tommy Hilfiger, while Prabal Gurung laminated silk and lace and presented hand-painted "raincoat" jackets.

Another key trend was cut-out dresses and cropped tops, with bared midriffs seen all over the runways from fashion prince Alexander Wang to American designer Jill Stuart.

While soft pastels were seen throughout the week, Lauren offered pops of bright color, with dresses in head-to-toe acid green, orange and fluorescent yellow.

Several designers mixed masculine with feminine, a look favored by Victoria Beckham, whose flirty, asymmetrical tennis skirts and loose pants revealed a new more relaxed side from the former Spice Girl.

Her two-year-old daughter Harper was unveiled as the new 'it' girl, drawing most of the attention in the front row as she bounced on her footballer father David Beckham's knee.

Wang, who was appointed creative director of Spain's Balenciaga last year, also blurred gender lines, pairing boxy tops with flirtatious skirts.

Michael Kors featured slashed dresses and slit skirts in his soft, romantic collection, and earthy colors of nutmeg and grass green that have been used by several designers.

Both "True Blood" hunk Alexander Skarsgard and actress Nicole Kidman took in Calvin Klein's show, after a star-studded week which saw appearances by hip-hop star Kanye West and pop prince Justin Bieber.

Curvy "Mad Men" siren Christina Hendricks and actress Christina Ricci were also spotted.

And in one of the biggest surprises of the week, 43-year-old supermodel Naomi Campbell made a rare catwalk appearance for Belgian-born designer Diane Von Furstenberg.