Mr Ewart had his degree safely at home after receiving it at a graduation ceremony at the Vodafone Events Centre in Auckland earlier this month.
Aquinas College principal Ray Scott said over the past nine and a half years, Mr Ewart had become an important member of staff.
"It was a great surprise to all of us when we heard he had completed a diploma," Mr Scott said.
"We had to celebrate afterwards, cake and everything."
Mr Ewart is the go-to man for photocopying, laminating and other IT and administration jobs, he said.
"He's always keen and looking for work. If John runs out of things to do he gets the message around seeking other tasks."