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Now the 55-year-old is going back.
Mr Chronican will start a new job as academic manager of the foundation year at the University of Otago on Monday.
''It's a university entrance course for international students and domestic students who don't have enough qualifications to get direct entry into an undergraduate degree.''
While Mr Chronican was ''really excited at the change'', he was sad to be leaving Kaikorai Valley College after 32 years at the school.
''Leaving is going to be tough.
''What I've really loved about here is the people. It's been about the people that have come in and out of here every day.
''I love the fact that they are full of promise and you know when you've been doing this a long time that you do make a difference to their lives.
''Kids come back and you find out later on that you were their favourite teacher and you made an impact. It takes a while to cycle back to you.
''I like that.''
Mr Chronican said he was not looking for a new job, but when the opportunity came up, he decided to take it.
''I thought, I'm 55, I want to be working at 65-70. I can either sit it out here or I can look for a whole new challenge.
''I'm happy with what I've been doing here - I love it - but I have been doing the same thing over and over. It's challenging, but there aren't any challenges that I haven't met before.
''I need to do something else in my life.''
He had accumulated a lot of experience and skills managing people and programmes during his time at Kaikorai Valley College, but felt it was time to use them in a different environment, he said.
Mr Chronican began his teaching career at what was then Kaikorai Valley High School in 1982, as a relieving maths teacher.
He was kept on and became head of maths in 1990 before taking on a variety of roles in the school's senior management, including student support director, assistant principal, deputy principal, learning support manager, and international student programme director.
He was also a successful First XV rugby coach during the 1980s, with his team winning the Dunedin under-18 competition in 1987.
He continued his involvement with secondary schools rugby at a national level throughout his time at Kaikorai Valley College and is the present chairman of the Secondary Schools Rugby Council.
Mr Chronican was also heavily involved in coaching rowing at the school for many years and was a keen participant in outdoor education activities, regularly attending year 10 Tautuku camps and school ski trips.
Principal Rick Geerlofs congratulated Mr Chronican on his appointment, but said the school was devastated to be losing ''a person who has given so much to Kaikorai Valley College''.
''Our loss is the university's gain.''