The student spoke to the headteacher and said she had been joking with her friends and it had gone too far, but revealed to her mother that what she had said to her friends was true.
Mr Harrison was arrested and he and the student were interviewed by police the following day.
He resigned from his role at the school in August 2019.
In August 2021 he was tried and acquitted of a criminal offence relating to the incident.
Mr Harrison denied the allegations and did not attend the TRA hearing.
The student told the panel she now realised she had been “groomed” and was trying to protect the teacher at the time.
In written evidence, she said: “My perspective now that I am older has changed.
“I realise that I had been groomed and manipulated and can see that I should not have been worrying about protecting Mr Harrison nor the impact that a prison sentence may have had on him.”
She also said: “I have gone through four years of hell… I am still scared of Mr Harrison and the potential that I may bump into him out in public.”
The student said the incident had had “a diabolical impact” on her.
The panel noted that Mr Harrison had “failed to recognise the devastating impact of his actions” on the student and her family and had a “complete lack of insight and remorse”.
The ban applies to any school, sixth form college, youth accommodation or children’s home, and he has no right to apply for his right to teach to be reinstated.