"Mr Sim always believed the boys of that day were too highly focused on sports and it was time to introduce arts, culture and academic achievement areas into school life. He always thought boys should have smarts as well as brawn," he said.
Mr Sim was always a hands-on principal and he would personally deliver the report cards to each student, accompanied by a perceptive comment on their progress or lack thereof, which left a deep impression on the recipients, he said.
The first school hall was named the Garth Sim Assembly Hall, which Mr Sim described as "the most important classroom in the school" and beams from the original hall can be found in a new theatre foyer, which also carries his name. Many of Mr Sim's charges have gone on to successful careers worldwide.
"We've had All Blacks and top cricketers come through but we've also produced men at the highest level of academia and in fields like medicine and law, as well as successful businessmen and just all-round good guys ... one of my great joys has been seeing so many of the boys who went through the college turn into men who contributed so much to society in such a wide variety of ways," he said.
Mr Sim has lived through two world wars, the Great Depression, and seen many technological advances during his lifetime, and while his speech might be a bit slower these days, he learnt how to email a year ago and still does the crossword every morning.
1914-2014 was a "great century to have lived" through, he said.
Mr Sim and his 94-year-old wife Nen whom he married in Bluff in 1941, still live in the same house they settled in when they moved to Tauranga in 1959 from South Otago. The couple had four children, and have 13 grandchildren, and 24 great-grandchildren.
He served in the Home Guard in World War II.
Born in Gore in the same year World War I started, Mr Sim and his late sister Gwen came from "farming-stock" and he did his primary schooling in Balclutha before attending South Otago High School - a school he would later return to as Rector in 1954.
After teaching, Mr Sim first worked in a HR role at Tasman Pulp and Paper Mill in Kawerau and then held positions at various accountancy and architect firms.
He officially retired at 84.