Meet the 11-year-old with designs on fashion fame

She can't quite spell her own name yet, but that hasn't stopped 11-year-old Cecilia Cassini from designing clothes and accessories for celebrities such as Miley Cyrus, Kelly Osbourne and Heidi Klum. While the Los Angeles tween may seem like a child prodigy, she is actually one of the growing "brat pack" of influential – if immature – bloggers and designers dominating the fashion scene.

Diminutive designer Cecilia Cassini, who began customising her own clothes at the age of six and now has a successful kids' fashion line, was recently snapped with a host of celebrities at New York fashion week. Cecilia, the daughter of a French fashion photographer and an American yoga teacher, has the wide-eyed looks of a model and is currently being filmed for her own reality TV show. Though she may be entrepreneurial, Cecilia's youth was highlighted in a recent TV interview, in which she misspelled her own name.

"We make sure she is grounded, that she does her homework before she starts sewing, and she gives money from the dresses to charity," said her father, Lionel Cassini, 42. "We're just supporting her, not pushing her."

The fashion industry has long favoured youth on the catwalk and in front of the camera, but it is an increasingly valuable asset behind the scenes too. Last month, Madonna's 13-year-old daughter Lourdes launched a fashion line, Material Girl, at the US store Macy's with her pop-star mum. But it is not just celebrities who are getting in on the act.

Last season, the 19-year-old Brazilian designer Pedro Lourenco took Paris by storm with a collection of leather dresses. Teen blogger Tavi Gevinson was hired by the designer label Rodarte – a favourite of celebrities such as Emma Watson and Keira Knightley – to promote its affordable collection for Target, and 17-year-old Jane Aldridge designed a line of shoes for Urban Outfitters on the back of her hugely successful blog Sea of Shoes.

Jessica Brown, editor of Drapers magazine, believes the rapid ascent of teen fashion stars is linked to the growth of social networking sites, which allow aspiring designers to tweet, blog and upload their designs straight to other youngsters. She said: "Young people don't pick up magazines like the previous generation did. They spend more time watching YouTube than TV, so it makes sense that retailers will connect with them through other young people."

The increasing number of young designers can also be linked to the explosion of the teen fashion market. Recent research from the retail analysts Mintel showed that one in five 16- to 24-year-olds spent more on clothes in 2009 than they usually would.

"Young people's continued desire to spend on clothing has created a great opportunity for these young specialist designers," said Tamara Sender, senior fashion analyst at Mintel. "Interest in clothes designed by teenage designers is growing."

However, some believe that the careers of young designers could be short-lived. Ms Brown said: "It is hard to say if they will have longevity. It's a great story for a kid to be doing a collection. Is it such a good one when they are 20? It all depends on the clothes."

Even young designers with the best possible connections fall foul of the competitive industry. In 2008, the Russian designer Kira Plastinina – who was only 15 when her clothing label expanded to 82 outlets – filed for bankruptcy in the US, at a considerable loss to her food entrepreneur father, who had invested $80m setting up the stores.

Jane Aldridge

Jane's shoe obsession led her to write the hugely popular blog Sea of Shoes, which sparked a collaboration with Urban Outfitters. The 17-year-old Texan managed to bag an invite to the Crillon Ball in Paris last year, recently hired an assistant and plans to study fashion at New York's Fashion Institute of Technology.

Tavi Gevinson

Despite describing herself as a "tiny 13-year-old dork that sits inside all day wearing awkward jackets and pretty hats", Tavi took the fashion world by storm with her blog Style Rookie, which has about 50,000 readers, appearing in the front rows at fashion shows and on the cover of Pop magazine.

Kira Plastinina

Kira became a brand when she was 14, developing more than 70 eponymous shops in Russia before expanding to the US at the age of 15. Despite an endorsement from Paris Hilton – rumoured to have cost Kira's father $2m – seven months later, the US division of her company filed for bankruptcy.

Lourdes Leon

The 13-year-old's junior clothing line Material Girl was inspired by mother and collaborator Madonna's early videos and film role in Desperately Seeking Susan. The line includes fingerless gloves and studded T-shirts, but stops short of the conical bra.