'Why am I leaving? Because the new man is already here,' Mr Ha joked over morning tea and biscuits with journalists on Monday, his penultimate day as principal of the school, a post he has held since 1968. But the veteran educator was showing no signs of last-minute regrets about handing the reins to his Australian successor, John Kennard, who has been working alongside him since January.

Strictly by the rules, Mr Ha's retirement is eight years overdue. Government regulations stipulate principals retire at 60 but direct subsidy scheme schools such as St Paul's are given more leeway in such matters and the school's managers were keen to hold on to him for as long as they could.

'I think, for Hong Kong, this is some kind of a record,' Mr Ha said. 'I was going to retire earlier but the school wanted me to continue. There always seemed to be one more thing to do. First it was until the school's 150th anniversary [in 2001], then it was switching to becoming a DSS school [in 2002] and then it was to spearhead the school's development projects.'

He will, however, stay on as education secretary of the school's sponsoring body, the Anglican organisation Hong Kong Sheng Kung Hui.

Mr Ha was just 31 when he took over at St Paul's, an unusually young age today. 'You could say that was quite young,' he admitted. 'These days you generally need to be in your 40s to get a headship because of the number of courses you need to have taken and the level of experience expected. In those days it was different though. School management had more autonomy.'

But one thing made his appointment even more unusual - he was Chinese. 'I remember walking into the school and seeing the wall with portraits of all the former heads hung on it,' he said. 'The whole lot of them were westerners - I was the first Chinese head of this school.'

It was the start of localisation for the sector. 'After my appointment, a number of other elite schools followed suit and hired local Chinese principals,' he said. The irony that he was being succeeded by a westerner, the first to be appointed to head a local school for many years, was not lost on him.

Mr Ha said he felt privileged to have been part of the 'special breed of people' that teachers were. 'As a teacher, you teach so many students and they go on to become the talents of tomorrow,' he said, history having been his subject. 'Can you think of three or four or five teachers who have left a really strong impression on you? If you can then you are really lucky. That human interaction has lifted up your life. For teachers, this is a source of great satisfaction.'

He gave the Mitch Albom novel Tuesdays with Morrie as an example of the way the best educators could influence their students' lives, by going beyond what was expected of them.

'All these teachers, they didn't have this when the schools hired them,' he said. 'These people are going the extra mile.'

Mr Ha has seen his fair share of changes and upheavals, both at the school itself and in the education system in general. As chairman of the Board of Education between 1990 and 1993, a member of the Education Commission from 1989 to 1993 and the education sector's representative in the Legislative Council between 1991 and 1995, he also played an active role in many of those changes.

One of the biggest for St Paul's was the switch from being a grant school to joining the direct subsidy scheme, in 2002.

With DSS funding, schools are given autonomy over how to spend their annual budget and have more freedom in the application of certain education policies, including the medium of instruction. They are also allowed to charge fees.

Mr Ha said this had given the school 'more space for being different'.

'The gains have outnumbered the losses,' he said. 'DSS schools are moving many years ahead of ordinary schools.'

Schools with more scope to experiment were healthy for the education system, as mainstream schools would benefit from their positive development.

'Although our fees are not so high, it has still meant we have been able to secure extra resources,' he said. 'We have introduced smaller classes, hired a large number of teachers from abroad and sent many students abroad as part of our global project. As a public sector school we would not have been able to do that.'

An increase in funds through donations has also enabled the school to improve its facilities. A $100 million wing to house a sports hall, indoor swimming pool and other amenities, is scheduled for completion by August.

Mr Ha will continue to keep an eye on the project. 'I'm still willing to help the school in any way I can anytime they need me,' Mr Ha said. 'I'll be very happy to help.'

But first it's time for a break: 'I have some close friends living overseas that I haven't had time to visit for many years. I'm going to go and see them first.'