The hearing was told that Elizabeth Pownall, 56, was sacked from Dayncourt school in Radcliffe-on-Trent, Nottingham, after she failed to satisfy an inspector's review of her teaching capabilities.
Mrs Pownall joined the school, now a specialist sports college, in September 1992 and was appointed head of maths.
Headteacher Philip Clarke said problems with her teaching became apparent in 1996 when an Office for Standards in Education report showed a "serious negative" for the mathematics department.
He said that by April 1999 it had become clear that her teaching was not improving and a decision was made to call in a local authority inspector.
When asked why her "incompetence" as a teacher was not detected earlier, Mr Clarke said: "If I can use the analogy of the Titanic, the ship became holed some time after 1992 but, because of the experience of the staff in the maths department at the time, it managed to sail on."
The problem only became apparent when experienced staff had been replaced by inexperienced teachers.
John Drydon, an inspector at Nottingham education authority, was asked to complete four reviews of Mrs Pownall's competence between March 2000 and October 2001. "There were both weaknesses in the teaching and leadership of Mrs Pownall," he said.
Mr Drydon said he had observed her teaching a Year 7 class, who were in the top set, multiplication by 10. "To multiply whole numbers by 10 is not what you teach the top set of maths in Year 7. She even finished the lesson by doing mathematical hangman. Her judgment that this was an acceptable way to end a lesson was not good - particularly since I was there.
"She also lacked consistency. On some occasions she forbade talking in class; on others even I was distracted by some pupils talking."
He said that after each review, improvements were outlined on how Mrs Pownall could improve. "After each review it was my opinion that she had not attained a satisfactory improvement in her teaching. In my view the key issue was whether the children had improved their learning in her lessons and they had not."
Mrs Pownall had not responded to suggestions made to her, and although being advised to visit another school's maths department, she only did so once.
Liz Paver, chair of the disciplinary panel, said the facts did constitute a case of serious professional incompetence. She said Mrs Pownall would be allowed to continue teaching if she successfully completed a refresher course within two years .