An "academically gifted" teenager killed herself in her parents' garden shed the day after being barred from an Orpington grammar school, an inquest heard.

Francesca Candita-Simpkins, from Catford - who told a teacher she'd had suicidal thoughts since she was six - was just 13 when she was found hanged in April this year, the hearing was told.

The teen, who planned to join the diplomatic service after studying at Oxford, was excluded from school for two days after stealing a craft knife from a design technology classroom at Newstead Wood School with a friend to become 'blood sisters,' the inquest heard.

The prestigious grammar school in Avebury Road failed to consider how excluding her would affect her - even though year nine pupil Francesca had attempted an overdose six months before and did not get on with her parents, Southwark Coroner's Court was told.

Coroner Lorna Tagliavini slammed the school for failing to consider the youngster's circumstances when they punished her and not following its behaviour policy.

The coroner also criticised the local mental health trust where Francesca had received treatment since 2008.

Francesca's parents, Edward Simpkins and Rosa Candita-Simpkins, told the inquest they did not know she was self-harming until her overdose or how to support her.

Talking about his daughter after her overdose, Mr Simpkins said: "All the conversations I had with Francesca, she made promises never to anything like that again.

"I honestly believed that she was too sensible to do something like that again."

At the beginning of November 2014 she confided in a teacher that she'd had suicidal thoughts since she was six, was self-harming again and did not get on well with her parents.

She was placed on a 'red flag' list to indicate to teachers that she was vulnerable and needed to be treated sensitively.

But the girls’ school failed to tell her parents - who believed her mental health was improving - the inquest heard.

Five months later, the day after she stole the craft knife on April 20, Francesca and her father attended a meeting with a teacher, who suggested if Francesca was to be suspended it would not be until the end of the week of exams she was about to complete.

But the then headteacher Alison Ross, who did not meet with Francesca or her parents, decided she should immediately be excluded, the inquest heard.

The next day she hanged herself at her home while her mother was out collecting her siblings from school.

Her father found her in the shed.

Police found a half-finished letter inside her room, which said she was sorry for letting her family down.

Coroner Lorna Tagliavini described Francesca as “a very bright student, academically gifted with a close circle of good friends”.

Criticising the school for the way it dealt with her suspension, the coroner said there was no evidence to suggest she was a threat to other students or took the knife to use in any way other than to become a “blood sister”.

She told the court: "Mrs Ross had already made her mind up and made the decision that Francesca would be suspended.

"On that basis I do find that the school's failings on that part have contributed to the events that occurred.

"It was the exclusion of Francesca from her school which she clearly enjoyed and where she had a great circle of friends.

"She did look up on the computer details about nooses.

"In order to be sure that Francesca committed suicide I have to be sure that Francesca intended to harm herself and that she intended to take her own life.

"Her letter does not mention that she intended to take her own life.

"It does say that she is very sorry and does refer to taking the knife.

"It's my experience that many people don't realise or appreciate the dangers of putting a noose round their neck.”

Recording a narrative verdict, she added: "This was an action of self harm contributed to by a failure to fully consider the implementation of their (Newstead Wood School’s) major behaviour policy and exclusion policy.

"I don't find that there was an causative or contributive factor by the mental health trust but there were some gaps in the care."

Both South London and Maudsley NHS Foundation Trust and the local safeguarding board are preparing reports into the incident, but the coroner said if she was not satisfied with their recommendations she would make her own report.