Jane Callister was so keen to stop the boy getting into trouble at school that she even took the knife back to his home.
The 46-year-old also invited the P7 pupil, thought to be 11 or 12, to her home to watch films and play computer games, and had contact with him on social media.
Miss Callister, who resigned from her job at Seafield Primary last year, in Elgin, Moray, appeared before the General Teaching Council for Scotland (GTCS) this week, where she faced five charges.
The case follows the death of 16-year-old schoolboy, Bailey Gwynne, who died after being stabbed whilst at school in Aberdeen in October last year.
Miss Callister accepted that her conduct, which related to the period December 2014 to June 2015, permitted a finding of impairment by the GTCS panel.
She told the hearing: “One day after school I was marking and went to collect jotters from pupil’s trays. In pupil A’s tray I discovered a small multi-tool with a knife attachment, like a Swiss army knife.
“I put it in my bag and never informed the head teacher as I felt it would be detrimental to pupil A. He was a bright pupil who came on a great deal in my class.
“I didn’t believe the acting headteacher and pupil A had a good relationship.”
She continued: “I spoke to pupil A at his house in front of his dad and gran and he said he’d been using it for his ‘den’. The pupil said he’d put it in the tray as he felt it would be safe there. He showed remorse and said he wouldn’t bring the knife to school again.”
She also discussed how she invited the pupil round to her house to play ‘Guitar Hero’ after feeling she had let him down when excursions had been cancelled.
She said: “It is true I invited pupil A to spend time with me on more than one occasion.
“I was aware from what pupil A had said to me that he was often left to look after his younger siblings at the weekends as his father worked late and he got bored.”
Ms Callister also used Facebook to contact the boy after she had resigned because she didn’t want him to think what had happened was “his fault”.
“While I accept it was an error of judgement, I would urge the panel to find that my intention was innocent,” she said.
Jane Hart, Case Presenter for the GTCS said: “You didn’t trust your senior management team to deal with it in an appropriate manner. You were judge, jury and executioner.
“Firstly, the conduct required deception, scondly it required an act rather than an omission, thirdly it required significant effort, it went against a written policy and finally it took place for a specific purpose.
“In my submission, the panel has unquestionable evidence that the respondent knew she should have disclosed the knife to the relevant people.
“Public confidence would be severely damaged if this conduct was not found impaired and the respondent deemed unfit to teach.”
The GTCS deemed that Miss Callister’s actions had not been in line with the codes of professionalism and conduct that a teacher should uphold and that her actions had been dishonest.
John Kilpatrick, Chair of the Panel, said: “The facts in this case have been established and Miss Callister has been dishonest in her actions.
“The panel have decided that the respondent is unfit to teach and the respondent’s name is to be removed from the teaching register.”
The panel will now issue their written decision within 14 days which will detail how long it will be before Miss Callister can apply to re-join the register
The decision to strike Miss Callister off the teaching register comes just two months after a schoolboy was jailed for nine years after stabbing his classmate to death in Aberdeen.
16-year-old Bailey Gwynne died after being stabbed in the heart whilst in class at Cults Academy in October last year.
146 young people under the age of 19 were convicted of handling an offensive weapon in 2014/15.