Graham Kitchin (61) retired early from the school after 38 years at the end of 2012, he said, because of management issues he felt were not likely to improve.
''I could not see myself making the same contribution as in the past to the school that I had valued so much,'' he told the Otago Daily Times yesterday.
Last week, Mr Kitchin sent a letter to the Ministry of Education outlining his concerns.
He was among 17 people who contacted the ministry in writing or verbally about the school.
Issues raised were pupil management, school communications, how the school managed concerns, and the wellbeing of pupils and staff.
He said they were being treated ''very seriously'' by the ministry.
On Tuesday, the high school board of trustees accepted an offer of help from the ministry amid the concerns.
The board also confirmed on Wednesday a senior staff member had been stood down over an alleged ''serious'' incident.
In an interview yesterday, Mr Kitchin said his letter was not a complaint, but provided information to ensure the ministry understood the issues.
He wanted the situation finally resolved because of his loyalty to the school and community.
Several teachers have left the school since 2012, some sharing similar concerns, he said.
Mr Kitchin did not know exactly how many had left but said the number was ''significant''.
Nor did he know if all had left because of management issues, but he could name six who had.
As the school's former specialist classroom teacher, Mr Kitchin had mentored other teachers and said those who had left because of management issues were ''top-class teachers''.
He had been contacted by ''parents, grandparents and friends of families'' of boys at the school about what was happening.
They were reluctant to get publicly involved or file complaints because their boys were still at school.
''Their comments tend to dovetail with teachers','' he said.
Mr Kitchen did not want to go into specifics which could identify individuals.
Late last year, about a dozen parents and some teachers met and expressed ''fairly strong concerns''.
Mr Kitchin has remained silent since he left.
But issues have become common knowledge in the community, and comments and rumours have been posted on social media.
Yesterday, the Otago Daily Times sent a list of questions to the Ministry of Education.
The ministry's head of sector enablement and support, Katrina Casey, said the 17 people who contacted it were parents, service providers, school staff and other community members.
They included conversations with some people who did not wish to make formal complaints.
They were referred to the board of trustees.
''Our expectation is that schools will promptly and effectively manage the complaints they receive, on the understanding we are here to offer support if required,'' she said.
The board had agreed to copy the ministry on all correspondence relating to concerns.
''We take all the concerns we've heard about Waitaki Boys' very seriously and want to ensure they are properly addressed,'' Ms Casey said.
''We are committed to working closely with them until all issues of concern are resolved to the satisfaction of parents and the wider school community.''
Ms Casey said the meeting with the school on Tuesday was constructive and the ministry trusted the board was equally committed to resolving the complaints and concerns.
Asked if the ministry had considered action under the Education Act's statutory intervention process, which can include replacing the board with a commissioner, Ms Casey said that would only be considered if the board was unable to govern ''in some important respect''.
Board chairman Garry McLeod did not want to comment until he had seen the ministry's response.
