The boys were practising parkour, an acrobatic way of overcoming obstacles, usually in the urban environment.
Twenty-seven-year-old Frederick William Mackie was in the video and had taught the teenage boys who featured.
Mr Mackie was a recognised athlete through New Zealand Parkour, had a degree in health and fitness and was a qualified personal trainer.
"Indeed the fear is always there, it's always present even right up to the point of jumping or flipping," he said.
"But [the] truth is that it's all a mental thing, so I teach people how to get past it and it's the same as in everyday life ... We can use all the bad things to do good."
He said the key to staying safe was controlling emotion and the surroundings as much as possible. He said he checked that no damage was done to the school.
Mr Mackie said while others would indeed try the sport, it was best to get formal training and he had never come across anyone who "did it out of stupidity".
"I don't encourage it nor do I appreciate or approve of people getting hurt ... Hence why I train them and teach them so those things don't happen," he said.
"It seems life threatening, even stupid to most, but what is life without risk and adventure?"
New Zealand Parkour chief executive Damien Puddle said most of what was shown in the video was good practice, but he did not support jumping on corrugated iron rooftops.
"Parkour is becoming more and more popular every year and we're working to try and ensure issues like this don't happen."
Mr Puddle was working on a PhD examining the development of parkour in New Zealand and said his organisation had been set up to connect people with the core philosophies of parkour, which included "leave no trace".