A teacher at an all-girls public school has been jailed for 15 months for conducting a secret sexual relationship with a pupil.
Emily Fox, who taught PE at the Royal Masonic School for Girls in Rickmansworth, Hertfordshire, exchanged hundreds of "sexually explicit" messages with the 15-year-old girl.
The pair struck up a friendship in November 2012 but from Easter 2013 developed an "intense" bond that involved kissing and later sexual touching, a court heard.
At one point the girl told the teacher she "loved her as a friend".
The relationship was discovered in August last year when a revealing email was printed out inadvertently and seen by the parents of the victim, who cannot be named for legal reasons.
Fox, 26, from Bath, pleaded guilty last month to four counts of engaging in sexual activity with a child while in a position of trust.
The first count relates to "touching by kissing", the second to "intentional touching of the child's breasts" and the remaining two to "digital penetration each to the other", St Albans Crown Court heard.
Fox looked upwards in the dock as as she was sentenced.
Passing sentence, Judge Stephen Gullick said he had no doubt she was a "gifted and well-loved" teacher.
But he said: "In my judgment, you were always aware that the relationship was not only wrong but also unlawful."
He said the sexual relationship lasted three or four months.
The judge said the teacher's reputation was "in tatters", and he accepted a jail term would be "extremely difficult".
But he stressed that "this type of behaviour towards pupils by teachers" must be seen as "extremely grave".
He sentenced Fox to concurrent sentences of one month on count one, six months on count two and 15 months on counts three and four.
Sally Mealing-McLeod, prosecuting, said contact between the pair began in November 2012.
She said: "Initially it was what one could really call a friendship, as such. However, that changed around Easter 2013 and ... became far more intense.
"(The victim) told (the defendant) that she loved her as a friend, that she cared for her, and after that it clearly turned into a much more in-depth relationship.
"It began with kissing one another... and then, a little later on, turned into more of a sexual relationship."
She said the relationship came to light when the victim tried to print an email but the printer did not work.
The prosecutor said: "A week later the father was using the printer when that particular document was printed. That clearly disclosed some sort of relationship.
"As a result the mother (of the victim) contacted the school and spoke to the headmistress."
When spoken to by police, the victim at first denied any relationship, the court heard, before disclosing it at a second visit.
Ms Mealing-McLeod said an "abundance" of evidence to support the charges was discovered in WhatsApp messages between the pair.
For example, in July last year, she said, there was "communication of a sexually explicit nature".
"There are hundreds and hundreds of those messages," she added.
After the email printed out, there were messages trying to work out how to "cover up" the relationship, the court heard.
Fox, who started working at the school in 2010, was charged after she attended a police station by appointment in September last year.
Dee Connelly, mitigating, said Fox had shown a "degree of bravery" in admitting the offences and felt "remorse and contrition".
She had wanted to be a teacher from a young age and accepts her "cherished" career is now ruined, the barrister said.
Fox took an overdose in 2011 and suffered depression after her parents moved to America, the court heard.
Ms Connelly urged the judge to take into account that the age gap between the two was "not that great" and also said the defendant had been "gravely concerned" about the impact on the victim.
Fees at the Royal Masonic School for Girls cost up to £25,000 a year.
The school was founded in 1788 to educate the daughters of Freemasons who were unable to support their families.
Fox was dismissed from her job after the allegations came to light.
In a statement on its website the school said a "robust recruitment check" at the time she was recruited showed she had no criminal record and she was "fully cleared" by the Disclosure and Barring Service.
It went on: "When the school became aware of the allegations, it immediately informed the police and suspended Ms Fox in accordance with its policies.
"Following Ms Fox's suspension she did not re-enter the school premises and, after an internal investigation into the allegations, was dismissed for gross misconduct."
The school said a recent inspection had led to no shortcomings or recommendations in relation to its practices or procedures.
It added: "The school is deeply saddened that this situation has occurred and has extended support to the victim and her family at this difficult time and they remain fully supportive of the school."