Collegiate became part of the state school system in January 2013 after a decision by Education Minister Hekia Parata in November 2012. It was later reported she disagreed with the decision but was overruled by Cabinet members, thus ensuring the school remained open. There has been criticism of the decision, given falling rolls in other Wanganui secondary schools.
Mr Moller's pragmatic about the day student cost of $10,000 to attend Collegiate, which he sees an investment in the child's education, and also in the school.
It is this funding that helps to pay for the maintenance of all buildings.
"Our day students can be here from 8am-8pm. They are in a house and are provided morning tea, lunch, stay for dinner and stay for prep."
They receive lessons, nutrition, exercise with sports and compulsory prep coaching after school.
"One of my visions here is to have the school going so well we can offer scholarships to help local kids."
But the school is not in a financial position to be offering places until it is a viable operation, Mr Moller says.
The school's budget is in the hands of its commercial manager, Rosemary Fletcher.
The former freezing worker says he would have loved to have been able to attend Collegiate, but it was not in the family's budget.
Instead he went to Waitara High School, and after six seasons at Borthwicks meat works in the north Taranaki coastal town where he grew up, he went on to Palmerston North Teachers' College. Mr Moller says his new position suited his skill-set and he has previously worked in integrated schools.
Catholic schools were the first to be integrated into the public system in the 1970s. Had they not integrated, they would likely have fallen over, he said.
Though not a Catholic, Mr Moller was deputy principal for nine years at Francis Douglas Memorial College in New Plymouth. For two of those years, he was acting principal and ran the school.
The difference between integrated and public schools is ownership, and how much each school gets under the system.
Public schools are funded entirely by the Ministry of Education (MoE) and every five and 10 years received large amounts of money for the maintenance of its buildings and lands.
Collegiate owns its buildings and land on the Liverpool/Grey St site, which is run by the Whanganui College Board (WCB).
"The Government funds staffing and operates salaries, and gives a little bit of money for the teaching buildings, maintenance and furniture."
Under the MoE guidelines on staffing, Collegiate does support extra staff, which is generated by international students and extra funding from the board.
The school's international students are a separate entity and not part of the integration agreement with the MoE.
All day students are affiliated to a boarding house. These houses are in the school's ownership and are paid for by students' fees and funds generated by investments.
The day school will be run by a Collegiate school board with elections for parent representatives to be held in May. A chairperson will be selected following the elections.
Mr Moller knows these are challenging times, but points to the school's "excellent programmes and a common room of excellent staff".
"We just want to add to it.
"We have the school running well and the foundation is something that is working fairly well for us ... but it's time to move forward."
"We are inclusive and we offer schooling-plus with a huge commitment from staff."
While young at 50, Mr Moller is not the youngest to have been in the role of headmaster.
He knows the English public school system, having been a housemaster at St John's Leatherhead, Surrey, where he taught for nearly five years.
He returned to New Zealand in 1999 with his wife, Isabel, who has a teaching degree from Cambridge, and their three children, in Years-8, 11 and 12.
Collegiate is a family school and suits the Mollers, who can live, teach and learn on-site.
He's striving for excellence across the board, and looking at all the things the school is doing.
"All the extra-curricular, the hours in the classroom and the hours outside." WCS has a six-day a week teaching curriculum, and then there are the sports and cultural extra-curricular.
He wants mass participation in the school and will continue to work on how to keep that.
Thirteen years' working in boys' schools (Francis Douglas and Hastings Boys' High) has set him up to be a firm operator.
He's proud of the 100 per cent NCEA level one and two pass rates by the girls in Years 11 and 12, and lifting the boys' rates is a clear objective.
Mr Moller pulls on his academic gown and gets ready for Big School assembly, with his parting words: "we have children of promise and they will leave here as young adults of character."
