Mackey told the tribunal that, in a class on April 13, 2016 the student disobeyed instructions and was "laughing at me as I was trying to speak seriously with her".
Mackey asked the girl to step outside.
"As we were stepping outside, she continued laughing which made me really angry by then so I pinned her up against the wall," Mackey said.
Another staff member who witnessed the incident told the tribunal that Mackey had asked the girl to stay behind after the class ended to write an apology letter for her behaviour.
"Before the end of the lunch break, she was instructed to read it back to Karlene, which she did," the witness said.
"Whilst reading, she read out that teachers need to earn her respect, which led into a heated argument between the two.
"There was swearing between the parties and it ended with [the student] telling [Mackey] to get f-----, before she ran out of the classroom crying. Karlene then followed her."
Another staff member said she saw Mackey "holding [the student] by the scruff of the neck holding on to the collar of her polo shirt, pushing her against the glass door".
Mackey, a mother of three who has been teaching for 12 years, told the tribunal that she was "unusually distressed on April 13 as the consequence of a financial issue and was distracted by the possibility that a debt collector might visit her at the school".
"The respondent stated that [the student] got her at her weakest point," the tribunal said.
Mackey said she apologised to the student later that day after realising that "I had a problem dealing with my anger".
The student's parents complained to the school the next day. The principal held a restorative meeting at which Mackey apologised to the student and her parents.
The school formally disciplined Mackey, issued her with a final written warning, and required her to undergo professional development and anger management counselling.
The student's parents told the tribunal in a letter that the incident "detrimentally impacted on [the student]'s behaviour and learning for six months".
"[The] parents in their letter assert that they are not confident that the respondent has the ability to 'exercise the self-control required of teachers', and say that she cannot be trusted to provide a safe learning environment for students," the tribunal said.
"They pose the question, 'Should Ms Mackey continue in the teaching profession?' and answer it, 'No.'"
The tribunal said it might have deregistered Mackey if it had heard the case sooner after the incident.
"However, the persuasive factor for us is that Ms Mackey returned to the classroom soon after April 13 and has, in the time since, taken steps to minimise her risk of repetition," it said.
"Having heard from her, we are satisfied that the respondent has genuine insight into what let her to physically abuse [the student].
"We accept her assurance that the programmes she has undertaken have assisted her to recognise and control the emotions that lay behind her actions."
