A teacher who "improved" her pupils' GCSE course work to make a good impression in her new job has been barred from teaching for four years.
Helen Bowen began teaching maths at Ysgol Preseli, Crymych, in 2005
Helen Wyn Bowen was teaching maths to a group of 16 students at Ysgol Preseli in Crymych, Pembrokeshire.
A General Teaching Council panel was told that checks showed that some pupils had their course work altered.
The panel decided that Miss Bowen, who has already been sacked, was guilty of unacceptable professional conduct.
Miss Bowen was not at the professional conduct committee in Cardiff.
The tribunal was told she had initially denied changing the work, but later admitted she had, and was dismissed for gross misconduct.
Some mistakes had been corrected - in one case the word "higher" was changed to "lower", and in another, "wasn't", became "was", the tribunal heard.
As well as her altering words and figures, the hearing was told she also wrote lines in pencil for pupils to go over them in ink.
In all, Miss Bowen, a teacher of 12 years' experience, altered a total of 21 GCSE course work papers submitted by the 16 pupils, it was claimed.
The hearing was also told she had given the pupils so much help that their work was impossible to reassess, so they had to be assessed on earlier years and most of them were marked down.
The school's deputy head teacher, Michael Davies, told the hearing that Miss Bowen was found out because her writing was "so distinctive".
''An act of cheating'
He said: "She claimed she did it for the benefit of her pupils and she wanted to make a good impression at a new school.
"When changes are made to course work it is an act of cheating. Her actions were unethical, unprofessional and amounted to gross misconduct."
Governors' disciplinary chairman Caerwyn Davies told the hearing: "There was an irreversible breakdown of confidence and trust between her and the school."
Miss Bowen had previously been acting head of maths at Bedwellty Comprehensive but lost that job when the school closed.
She started working at Ysgol Preseli in September 2005 after the previous teacher retired, and had been responsible for a group of intermediate level pupils.
The General Teaching Council professional conduct committee gave her a prohibition order and she will not be allowed to apply for registration as a teacher for four years.