In a file note, the tribunal said the Education Act did not "distinguish between acts that occur in a school setting and those that take place in a private context".
Quoting an earlier decision, it said the tribunal must consider whether "a teacher who has engaged in a behaviour prohibited by the rules - whether it took place inside or outside the work environment, and whether or not it attracted a criminal conviction - is fit to remain a member of the profession".
An agreed statement of facts said Sami hit an adult family member who had been living with her and her husband since he came to New Zealand from Samoa in 2014.
"When the victim asked to live elsewhere, Ms Sami told him he would be returned to Samoa," the agreed statement said.
"Ms Sami stated: 'I felt a sense of disappointment, as [the victim] knew very well the trouble we had went through to get him here to New Zealand. I accept I told him he would return to Samoa, as that was our original agreement.
"'As a result, I picked up whatever I could find and began to hit the victim.'"
The statement said Sami "picked up the steel vacuum cleaner pipe and walked over to her victim and struck him approximately five timers, including hitting him on the top of his head".
"She raise the pipe in the air with both hands and then swung it down towards [the victim]'s head," it said.
"The victim sought to defend himself by blocking the hits with his arms and suffered abrasions and bruising to his arm. Ms Sami's husband intervened to stop the assault by taking the pipe off Ms Sami."
Sami, who was 61 at the time, did not have any previous convictions and completed a 12-session anger management course.
But the tribunal said it was "unfortunate" that she did not inform the Education Council about the charges, which were only discovered through a police check when she applied to renew her teaching certificate.
"Practitioners should not assume that a discharge without conviction will ensure that the council remains unaware that there was a criminal proceeding," the tribunal said.
"The primary motivation regarding the establishment of a penalty in professional disciplinary proceedings is to ensure that three overlapping purposes are met.
"These are to protect the public through the provision of a safe learning environment for students, and to maintain both professional standards and the public's confidence in the profession."