Jessica Ellen Cornish was born in Chadwell Heath, London,^[9] to Rose (Archer) and Stephen Cornish. She was educated atMayfield High School in the London Borough of Redbridge. She attended Colin's Performing Arts School and as an 11-year old she was cast in Andrew Lloyd Webber's West End production of Whistle Down the Wind.^[10][11][12] She subsequently joined the National Youth Music Theatre and appeared in their 2002 production of The Late Sleepers.^[13] Jessie has two sisters, who are five and seven years older than she is, who were both head girls at school. Unlike her academic sisters, Cornish has stated she was "never really that good at anything". She said, "At school they were like 'oh, you're a Cornish girl' and they kind of expected me to be the same as my sisters. Give me something to draw or an outfit to pick for someone, or hair, make-up, acting, write a song, I'm fine with it, but anything to do with sums – it was never my thing." She also said she never based her intelligence on her exam results.^[14] She also said she was always good at singing and it was her "thing". In 2003, aged 15, she won Best Pop Singer in the TV show Britain's Brilliant Prodigies, performing as Jessica Cornish.^[15] At the age of 16 she began studying at the BRIT School and at 17 she joined a girl group named Soul Deep.^[16]She graduated in the class of 2006 along with singers Adele and Leona Lewis.^[17] At 18, she suffered a stroke as a result ofWolff-Parkinson-White syndrome, a condition that had been diagnosed when she was 11.
   Jessie J was signed to Gut Records, recording an album for the label, but the company went bankrupt before any material was released.^[12][16] She then found success as a songwriter, gaining a Sony ATV publishing contract.^[19] She was also the support act for Cyndi Lauper during Lauper's UK dates of her 2008 Bring Ya to the Brink tour (Lauper invited J to join her on stage for the performances of "Girls Just Want To Have Fun"). Jessie has also written lyrics for artists such as Chris Brownand Miley Cyrus, including "Party in the U.S.A.".^[20][21] Jessie J was also part of a girl band, called Soul Deep, for two years, however, believing "it wasn't going anywhere," she left the group. Despite people thinking that her first notoriety was through YouTube, Jessie was signed for four years before her first video was posted. Jessie first came to the attention of Lava Records when her publisher at Sony/ATV, Rich Christina, sent Lava president Jason Flom a link to her MySpace page, which the record executive loved.^[22] After seeing an impressive U.S. showcase, Lava, along with several other labels, was keen to sign the artist but progress was hampered by her management's insistence on, what Flom called, a "crazy deal", and their refusal to let Jessie speak to any labels directly.^[22] Despite this, Senior Director of A&R at Lava, Harinder Rana, made surreptitious efforts to meet Jessie on her own in winter of 2008. Later in the year a change in management to Sarah Stennett and Nadia Khan of Crown Music allowed record deal negotiations to take place. Jessie eventually signed with Lava as part of a joint venture with Universal Republic.^[22]