"We are in discussions with the headmaster and have instigated disciplinary procedures.
"As employers It is not appropriate to make any further comment until those procedures are complete."
Alumni of the school include Prince Edward, Formula One racer Chris Amon and current mayor of Whanganui Hamish McDouall.
On October 21, Mr Moller - who has been headmaster at Collegiate for three years - was driving down Liverpool Street in Whanganui, taking friends home because he thought he would be under the limit.
A routine police breath test found Moller was over the limit and a subsequent blood test recorded 106 milligrams of alcohol per 100 millilitres of blood.
The legal limit is 80 milligrams of alcohol per 100 millilitres of blood.
In Tokoroa court this morning, Judge Anthony Snell said Moller had made an "error of judgment" when trying to help friends by thinking he was fine to drive.
When asked if he wanted to say anything Moller acknowledged he had "made a mistake" and had gone through the court processes.
He had earlier pleaded guilty at a Whanganui District Court appearance in November but had the sentencing moved to Tokoroa because he spends a lot of time at a property in the area.
Judge Snell sentenced and disqualified him from driving for six months.
He was also fined $750 plus $135 for court costs and $189.25 for medical costs incurred.
