Many people referred to the data as "ropey" - a reference to a word Prime Minister John Key used earlier this year when he described the national standards information as "ropey at best".
NZ Principals Federation president Paul Drummond slammed the Government's move, saying what teachers and schools had feared the most was already happening.
Mr Drummond said the "ropey data" was one-dimensional and was unfair to students who were now being labelled as failures, but who might well be actually improving on their own personal levels.
"This is collated from data that the profession has been saying all along is unreliable. It's ambitious to make conclusions from this.
"You will create competition amongst teachers and schools. It's taking away the focus from what really matters - student progress," he said.
The NZ Educational Institute said it was disappointed that the information was being displayed as a go-to system for parents.
Vice-president Frances Guy said it was unfair to let parents think their child was failing, when in reality they might actually be improving.
"If you think about drawing a line in the sand ... a child just needs to be slightly below that line and they're not achieving.
"That child may actually haveEnglish as a second language and had come to school not knowing anything and they've done really well at that point. But because that is the standard and they are still below it, theyare failing. That is unfair," Mrs Guy said.
"[The data] is ropey. It's going to be dangerous and misleading."
Labour's education spokeswoman, Nanaia Mahuta, also used the word "ropey" but went further and said the decision to release the data was "pig-headed".
Shifting adds to pupils' difficulties
Gael Vickers, principal of Ruapotaka School in Pt England, Auckland, says there are many reasons some students are struggling with National Standards - and they can't be simply split into rich and poor.
Her school, with 200 pupils, faced a number of challenges that were being replicated around the country.
"I guess because I'm a decile one [school] in the middle of Glen Innes with a very shifting population - and that's one of the biggest issues. The children we get have been to a lot of schools."
Mrs Vickers said one Year 4 child who enrolled about a month ago had been to four schools.
"I don't personally believe it's necessarily the difference between rich and poor but it's often the circumstances like that, like the shifting populations.
"I think a lot of the houses are very overcrowded so there isn't the same parental support in some areas ..."
She said parents at her school had always known how their children were doing. "Even when it wasn't called a National Standard." She said that was very important and always had been.
Mrs Vickers said her issue with the standards was that there wasn't a national test, "so how can it be called a National Standard?".
"If you're going to call it a National Standard it's got to be the same everywhere. That would solve the whole thing."
She acknowledged that writing had emerged as a weakness for her school and believed that for many students it was because English was a second language. "A lot of them have very little or no preschool so they come in much lower, so it takes longer to get up there."
She thought children who did not switch schools regularly got up to speed more quickly than those who moved often. "Every time you move you're back two steps."
