Joyce Garner, a teacher at Thatto Heath community school, St Helens, put key stage 1 writing tests in a bin, and gave pupils too much help with an alternative task.
She was found guilty of unacceptable professional conduct by England's General Teaching Council and suspended for two years.
The panel heard how, on April 1, 2004, Miss Garner, who had been a teacher for almost 40 years, had arrived at the school distressed and was sent home.
The hearing was told how, on learning that colleague Paul Swift had taken her class that day, Miss Garner disposed of the papers believing pupils had been disadvantaged by a change of teacher.
Colleen Taylor, headteacher, said repetition of the original test meant that a new activity was needed to assess pupils properly .
Mrs Taylor said: "On the day the task was due to take place I noticed a handwritten A5 sheet of paper on Miss Garner's desk.
"It appeared to be a model answer for the 'jam sandwich' activity. It started with the sentence, 'First I washed my hands' which was consistent with the task to be done that day."
Mrs Taylor said that of 22 papers, 11 had achieved level 3 which was well above average, and there was also a striking degree of similarity between the pupils' work.
She added: "Thirteen of the papers began with the same sentence, and many included similar vocabulary.
"In all of the papers, punctuation and spelling was correct and 18 out of 22 were entitled 'my jam sandwich'."
Mrs Taylor also said that it was wholly out of character for some of the children to use the vocabulary they were using.
On May 20 a further writing activity, entitled mask-making, was carried out by Catherine Harrison, an independent assessor, for comparison.
The results were not consistent with the earlier grades.
Mrs Taylor said: "Out of the 11 who had previously achieved a level 3, only one obtained this grade in the activity carried out by Ms Harrison."
Miss Garner was suspended on June 24.
Mrs Taylor told the disciplinary hearing that Miss Garner denied telling the children what to write in the test, but admitted throwing away the original test papers.
Tony Neal, who chaired the hearing, said: "Maintaining the integrity of the Sats system is vital and Miss Garner has failed to show sufficient insight into the seriousness of her behaviour."