"And I'm not a businessman, I'm a principal and a teacher who cares passionately about the learning of the children."
And he is critical of National Standards, against which every child's progress is measured, arguing they are unjust.
"It doesn't work. It's unfair and certainly doesn't give an indication of the true progress a child has made."
Mr Priest said he had taught so many children who had worked hard and made enormous personal progress, but if they didn't come up to the National Standards for their age, "they are not recognised".
"It upsets me, it really does, because I know how many of these kids have big challenges in their lives and how hard they work. I'm tired of it, I really am ... I can't do it any more.
"I am giving up teaching. It's just so different now."
Even though he is unsure where his new career will be, he is hoping it will be something involving children.
"I enjoy children, and I want to still work with them in some way."
Yesterday a special assembly at the school was crowded with parents, students, staff, former pupils with their children and members of the community.
According to staff, it was highly charged and emotional, with everyone bursting into tears - including Mr Priest.
He was presented with a hard-bound book in which were photographs of all 105 students. Each had written him a personal message.
The messages included: "You showed me the baby chickens"; "You listen when we are sad and you play games on lots of days with us"; "you teach people to be nice to each other"; "You take care of us ... thank you, Mr Priest."
He is also bothered by how parents and communities judge a school by its decile rating.
"A school is about the education the children are getting - not about how wealthy the community is or isn't. But people just don't understand this.
"This is a decile one school, and I've stayed here for 24 years because I love the children and the community."
Previously, he had been teaching for three years at a decile 10 private school , he said.
However, he will be back to organise the hugely popular annual Wanganui Schools Cross-Country Event at Aranui School in 2013.
"Well ... it will depend on my [new] job and if I can get time off."
But the one thing he won't be doing is leaving Wanganui.
"Definitely not. I would never leave Wanganui ... ever."
Mr Priest's criticism of the new direction of schools comes hard on the heels of Wanganui Intermediate principal Charles Oliver saying the National-led Government was in league with right-wing governments throughout the world with a plan to create a crisis in education and impose competitive business models in "our world class schools".
The comments were made on November 20 at primary teachers union stop-work meeting.
