"There were no policies or procedures in place around working from heights, or for student involvement in the use of the scaffold," Worksafe's chief inspector investigations Hayden Mander said.
"With no safe systems in place students and staff were exposed to a very real risk of injury and this incident could have had catastrophic consequences."
The judge sentencing Forest View ordered the school to pay reparation of $100,000.
The judge also ordered the Forest View High School board to prepare and present a safety presentation at the National Conference of the School Trustees Association in 2020.
The board was also required to prepare a safety article for New Zealand's online school bulletin, He Pitopito Korero.
The board, in a statement, said it acknowledged "the seriousness of this incident and its impact on the victims, their families and the wider community".
"The board deeply regrets the harm caused and acknowledges that no injury to any student or employee is acceptable. As a result of the incident, the board apologised to the student, teacher, and their families and ensured that it provided ongoing assistance to them, including reparation payments and managing and supporting their return to work and study.
"The board has also fully co-operated with the authorities throughout the investigation and prosecution and taken a number of remedial actions to ensure such incidents do not occur again."