In June 2014 he was caught driving while disqualified and was again convicted and fined $500.
He did not inform the Education Council about these convictions, as he was required to do, but the council discovered them when he applied to renew his teaching certificate in August last year.
While the council was investigating these convictions, the school informed the council that Korau had used the school van last December for personal use but coded the cost of the fuel against his departmental budget.
"Mr Korau acknowledged he had been using the school van for personal use and, in explanation, advised that his partner had the car for their newborn child and he didn't have access to another vehicle," the tribunal said.
"Mr Korau said he viewed his visit to whānau who were considering sending their son to Napier Boys as school business and therefore did not use the appropriate code."
About the same time, in November and December last year, Korau was found to have communicated with other users of the NZ Dating website "when he was supervising students - not teaching, but during his hours of employment".
"The school issued Mr Korau with a final written warning as a result of their investigation," the tribunal said.
"Mr Korau stated he was experiencing some difficult personal issues, and became entrapped in a messaging relationship with a female user of the site.
"Mr Korau was co-operative with the school and the council and has sought counselling since."
The tribunal noted that it had "said in previous cases that even one conviction for a drink-driving offence places a teacher's registration in jeopardy".
However, in this case the offending occurred three years ago, there was no evidence that Korau posed a risk to his students' safety, and there was "no suggestion that the respondent has an ongoing issue with alcohol", so the tribunal decided that censure was "a proportionate penalty".
It found that the undisclosed personal use of the van and the use of the dating website while in class did not constitute "serious misconduct" in themselves.
"There is no evidence to suggest that any of the students he was supervising were aware of the respondent's actions," it said.
But it said Korau "conceded that his behaviour, considered overall, amounts to serious misconduct".