David Polden, 35, was teaching at Parliament Hill School in Highgate in early 2021 when he was arrested on suspicion of engaging in sexual communication with a child.
In 2023 he was found guilty of the offence at Wood Green Crown Court but avoided prison when he received a suspended sentence.
Last month the Teaching Regulation Agency (TRA) concluded that Polden should be banned from teaching in England for life.
Polden was initially deployed to the all-girls secondary school as an agency worker in 2017 before he became employed as full member of staff in September 2018.
In May 2021, the school discovered a conversation threat on its intranet system between Polden and a pupil.
The conversation contained a series of messages over a period of five days which developed into sexual messaging.
The school informed the Met Police and Polden was arrested.
When he was sentenced, Wood Green Crown Court heard that Polden had been warned by the school months earlier to avoid meeting pupils alone.
Sarah Creasey, headteacher at Parliament Hill School, said: “We take safeguarding extremely seriously, so this case was deeply upsetting for our school community.
“The staff member’s conduct represented a serious breach of trust and professional standards.
“The incident was quickly identified through our robust safeguarding procedures, and we fully cooperated with the police investigation.”
Sarah Buxcey, decision maker at Polden’s TRA misconduct hearing, said there was no evidence that he had shown any remorse or insight into his actions and the impact they may have had on the pupil..
Ms Buxcey said this meant there was a clear risk of repetition in the future.
It was therefore decided that his ban from teaching should be indefinite and he should not be entitled to ever apply for restoration of his eligibility to teach in the England
