"It's a spectacular school, and a huge amount of emotion went into making the decision to move.
"It's such an amazing crew of students and people and community."
He said whoever the next principal was would enter a school that achieved good results, had fantastic facilities and good financial backing here to do what they would like for the future of the school.
"I think there will be some strong respected candidates for the role here."
Harper finishes at Cullinane at the end of the second school term and moves during the school holidays after that.
The Board of Trustees at Cullinane will be recruiting Harper's successor, which can take a couple of months.
"It's important to finish my time here well and to leave with fantastic memories in my heart."