Parents pay an average of more than $2 million for a house in the Auckland Grammar School zone - but some of its students say the school apparently can't afford to keep its toilets clean.
Unnamed students at the school have started a petition on the California-based website change.org to get new toilets at the school.
"Stinky, dirty, disgusting, mosquito-infested bathrooms that obviously are not properly taken care of deteriorates the school's environment and makes the school feel like a prison," the petition says.
But headmaster Tim O'Connor says the school has already gone out to tender for a $100,000-plus contract to upgrade the main toilet block and add 10 extra toilets to it by the end of next term.
"If students are concerned about the condition of toilets, then my first response would be come and tell us about it," he said.
"I haven't seen the petition, you have just given me an introduction to it, I don't know anything about it, so I'm assuming they are not overly serious."
The decile 9 boys' school is New Zealand's sixth-biggest school with 2502 students at the end of April.
The median price of a three-bedroom home in its school zone in February was the highest of any school in the country, at $2.09 million.
But by 5pm today, 2195 people had signed the petition for new toilets, which has been promoted through a Facebook group for current and former students.
Year 12 student Giovanni said the two main toilet blocks had been dirty and smelly at least since he started at the school in 2014.
"The smell is very unpleasant. It can be smelt without even being inside," he said.
"Some of them don't even have locks. Some of them don't even have toilet paper.
"It's a combination of the students not being responsible and I have been to school multiple times in the morning and they haven't been cleaned.
"It's surprising that this is apparently the best high school in the country, yet we have terrible toilets. You can find the same or better toilets in public schools in less developed countries."
Another supporter commented on change.org: "How a 'top NZ school' can be regarded as such, with toilets similar if not worse than that of a prison's is beyond comprehensible to me.
"You begin to realise, over time, that management does what is in their best interest, disregarding the needs and interests of students. They treat it as a business rather than a public service."
However O'Connor said improving the toilets was the school's "next highest priority" after opening a new $6.4 million classroom block in May 2015.
"We demolished the Taj, which was the original toilet block on site, in 2014 to make way for the new classroom block, and then we have allocated just over $100,000 to renovate the toilet block in the main block," he said.
"It has been in the Ministry of Education's five-year plan for property, and it's going through a GETS [Government Electronic Tender Service] process at the moment."