They now cover the front entrance archway for both pupils and staff, and will be there for at least three months while significant structural work is done to stabilise the Archway.
Rector Richard Hall said the structure was designed in the 1940s and was never meant to have car traffic through it.
"It was for foot traffic only.
"Over the years, as the amount of cars coming through the school has increased, it has started subsiding and twisting.
"It’s not a danger, but it is obviously not in the solid state that it should be in."
He said the board decided to refurbish the archway alongside the development of the school’s Shand Building and grandstand.
"We wanted to preserve the traditional look of the school.
"The archway has got very special memories for us. Over 230 old boys who were killed in World War 1 are remembered there."
He said construction company Naylor Love would dig underneath the archway and repair the foundations. Steel rods would be inserted into the structure itself to make sure it was stable and earthquake-proof.
The project was being funded by the Ministry of Education.
"We’re really grateful that they’ve seen fit to support it, because it’s not their usual [practice] to support heritage work.
"It will cost about $100,000. It’s not a small project."
For the duration of the work, the only traffic access would be via the London St service entrance, he said.
"Please be aware that this is our only emergency exit and entrance.
"At all times, including weekends, we ask parents to drop off and collect your son further along Arthur St, or use Queens Dr to avoid congestion."
