The teacher, Connor McKenzie, admitted the charge, which related to an incident that took place at the unnamed school in May 2023.
Mr McKenzie no longer lives or works in Invercargill.
The decision by the New Zealand Teachers Disciplinary Tribunal about the incident was released last week.
A complaints assessment committee had been established to investigate the matter after the school’s principal filed a report to the Teaching Council of Aotearoa New Zealand in June 2023.
At the end of its investigation, the committee laid a charge that on May 18, 2023, Mr McKenzie had "used his hand to make contact with Student A’s face".
In its summary, the committee stated a lolly jar went missing from Mr McKenzie’s desk and he believed Student A and others were involved.
He approached a group of year 10 students about the jar and said he believed Student A knew who the culprit was and asked for the jar to be returned.
The pair argued for a time and then Mr McKenzie "quickly open-handed slapped Student A with his right hand across the left side of Student A’s face".
One of the year 10 students reported the incident to two staff members.
Student A later described the hardness of the slap as being a five out of 10 on a scale of one to 10, with 10 being the hardest.
He said the slap left a mark on his face for about three seconds.
He experienced shock in response to the slap, and the other students present also experienced shock and anger in witnessing it.
Mr McKenzie provided a statement to the tribunal in which he reflected about the incident and expressed his deep remorse for his actions.
He also provided an affidavit in support of an application he made for permanent suppression of his name and identifying details.
The tribunal found Mr McKenzie did use his hand to make contact with Student A’s face in May 2023 and fell "significantly short of the standards expected of registered teachers who work in New Zealand secondary schools and that his conduct was serious misconduct".
The tribunal denied him permanent name suppression.
It did not consider the gravity of the conduct was serious enough to warrant cancellation of Mr McKenzie’s registration, which was set to expire in January 2028, or for a suspension order.
The tribunal made orders of censure and imposed conditions on Mr McKenzie’s practising certificate, which would be noted on the teaching council register for two years.
He was also ordered to pay $2336, which was 40% of the costs incurred by the complaints committee in its investigation and prosecution.
— Allied Media
