Disgraced Hartlepool teacher David Fenwick had been questioned before at his school about his “over familiarity” with pupils.
Fenwick, now 44, has been banned from classrooms for life for an affair with a 16-year-old pupil after kissing her at their Wearside school's prom night.
A National College for Teaching and Leadership misconduct panel was told that he had “been spoken to informally on four occasions” during his 13 years there.
Its report notes: “Mr Fenwick’s previous conduct at the school has raised concerns about his ability to maintain appropriate professional boundaries with pupils.
“This led to Mr Fenwick receiving advice from his head of department and headteacher on separate occasions and culminated in him being provided with additional safeguarding training.
“However, despite this Mr Fenwick still went on to devleop an inappropriate relationship with Pupil A which commenced whilst she was still a pupil of the school.”
A teacher since 1996, Fenwick was originally employed in the special educational needs department at the school in November 2002.
A number of official investigations were launched after the school became aware in 2015 of the allegations against him.
A statement from the school after the ban was issued read: “Governors are confident that safeguarding procedures within the academy are robust.
“They are checked regularly and externally reviewed and evaluated and judged to be consistently excellent.
“The academy reported all allegations relating to Mr Fenwick’s behaviour to the appropriate authorities as soon as they became aware of them.
“The governors instigated immediate disciplinary action.
“All policies and procedures were followed rigorously and Mr Fenwick was summarily dismissed from his post.”
A Northumbria Police spokeswoman said: “We are not investigating this matter.”