He also had extensive experience teaching in New Zealand state schools so he's been equal to the task.
However, the upgrading the school buildings has added a new dimension to the job. Almost all the buildings at Collegiate have heritage status and then there are earthquake strengthening requirements.
In a recent interview with School News magazine, Mr Moller said he felts privileged in his role.
"I feel as though I have inherited a classic old car and have been spending time tuning and modernising the engine," he said.
To the casual observer, Collegiate still looks like its 162-year-old self but there have been some significant changes inside the buildings.
The science block in Liverpool Street was strengthened and refurbished last year to be re-opened as the Sir Harold Gillies Science Centre with state-of-the-art facilities.
The library is currently being renovated and there is new carpet and furniture in most of the classrooms.
Mr Moller said all the costs of strengthening and renovations would be met from attendance fees.
A new administration block is to be built on the Grey Street side of the school grounds.
"That will be the admin entrance. We have the chapel entrance in Liverpool Street but, because we occupy an entire block, people are never sure where to come in."
Welcoming the community in to Collegiate is important to Mr Moller and he is proud of the tikanga learning that students experience with Whanganui iwi.
The ERO report commended the school's progress in building a "bicultural ethos" and te ao Māori view in the school.
The current roll of 396 consists of 56 per cent male and 44 per cent female with 46 Māori students.
There are 302 students boarding at the school and Collegiate has hosted 54 international students in 2016.
Mr Moller said Collegiate was also encouraging students in extending goodwill out to the community.
"Boarders are here seven days a week and they are willing to help out in the community so we welcome inquiries," he said.
The aim is for Collegiate students to become well-rounded people who achieve to the best of their abilities and show concern for others.