A singing teacher at a prestigious Roman Catholic boarding school had sex with a sixth former after giving her free lessons and sending her a picture of him in the bath.
David Brown, 46, also encouraged the 18-year-old to take drugs after telling her how much they would boost their sexual relationship.
The relationship was only discovered after the schoolgirl's mother found messages on her iPhone - which Brown had given her - and on a laptop which discussed their sex sessions.
Brown, who worked at Worth School in West Sussex, was banned from the classroom for life after admitting unacceptable professional conduct and conduct which may bring the profession into disrepute.
The school, where fees for boarders reach £32,000 a year, is renowned for its music, and has subsequently developed a well regarded music department.
A professional conduct panel of the National College for Teaching and Leadership in Coventry heard between 1 June and 31 December 2015 he sent the girl, identified as Pupil A, messages encouraging her to take drugs, indicating he had taken them.
He also sent her a picture message of himself in the bath, messages which were of a sexual nature and had sex with her on one or more occasions.
Self-employed Brown had been contracted to work at the school as a teacher from 24 September 2012.
The pupil's mother, named at the hearing only as Parent Z, was shocked when she looked through Pupil A's iPhone which contained messages exchanged with Brown.
The texts were extremely explicit and quite often [Mr Brown] would text her to switch to WhatsApp as it was safer
Parent Z said in a statement: "The messages again included open references to drug use and even offering to share them with Pupil A.
"Mr Brown referenced the 'come down' and also the great effect drugs could have during sex."
The panel also considered the contemporaneous text message Parent Z sent to Brown that December where she referred to his 'coke' use. Pupil A told the school: "Mr Brown emphasised the good aspects of drugs if taken in a controlled environment." The girl has since left school.
Parent Z said she looked through Pupil A's laptop which contained a large volume of messages exchanged between Brown and her daughter dating back to February 2015.
She said: "Pupil A's tone was one of trust … it seemed Mr Brown was praying on her vulnerabilities."
She explained: "The text messages quite quickly escalated into flirtatious chat and by the summer of 2015 Mr Brown had sent naked images of himself in his bath to Pupil A."
Parent Z said "the texts were extremely explicit and quite often [Mr Brown] would text her to switch to WhatsApp as it was safer."
The panel considered the relationship between Brown and Pupil A arose as a result of their contact at the school and therefore could be categorised as a pupil/teacher relationship.
Parent Z said "it was clear a physical relationship had begun as there were explicit references to Pupil A and Mr Brown having had sex within the text messages".
Pupil A said she started having sex with Brown at the start of July that year. Brown said it was not whilst she was a pupil at the school.
Panel chair Mr Michael Lewis said: "The panel also noted prior to the sexual encounter, Mr Brown provided Pupil A with free singing lessons, a part time job and then later, bought her an iPhone on which they could communicate.
"The panel considered the school's note of their meeting with Pupil A, where she discussed the sexual encounter noting she was 'very conscious of the end of term."
They decided it was more probable it happened when she was still at school but in any event it arose from the relationship that developed whilst she was a pupil.
Mr Lewis said: "The panel also considered that the provision of the free singing lessons and the paid part time job, could be seen as an attempt to foster a relationship, which the panel regard as inappropriate."
He added: "The panel is satisfied that the conduct of Mr Brown, which involved sending inappropriate messages to a pupil which included encouraging her to take drugs and messages of a sexual nature, and engaging in sexual activity with the pupil, fell significantly short of the standards expected of the profession."
Brown was prohibited from teaching indefinitely which means he cannot teach in any school, sixth form college, relevant youth accommodation or children's home in England.
Decision maker Ms Jayne Millions, on behalf of education secretary Justine Greening, said the case was so serious Brown shall not be entitled to apply for restoration of his eligibility to teach.