Some parents of underperforming students have been told to keep their children home from school over the next three days of NAPLAN testing.

Thousands of students around Australia in years 3, 5, 7 and 9 will be sitting the national literacy and numeracy tests over the next three days.

But schools are being accused of "going mad" over NAPLAN because of fears the test results could be used to compare schools.

Even as tests get underway, parents and education unions around the country have raised concerns over how the tests are being conducted and how the results will be used.

Queensland Teachers Union (QTU) president Steve Ryan says he is aware of cases of schools encouraging students to stay home on testing days under the NAPLAN "regime".

"Unfortunately the emphasis put on the NAPLAN tests themselves, the nature of the high-stakes testing is dragging schools into what I would call unwanted practices," he said.

"[It's] not just students who may be told to stay at home. It's not just that sort of situation that is an issue here."

There have also been reports of particularly bright students being offered transport to school on testing days and reports of schools "grooming" students to perform better in the tests.

Leah Thomason says she was told her son, who is in grade 3 at Mount Cotton State School in Queensland, will be exempt from the test.

"Last Friday afternoon when I went to pick them all up from school, two of my children handed me forms," she said.

"One of them said that they were getting special help with the NAPLAN test and the other said that they were being exempt."

Ms Thomason says when she spoke to the deputy principal about the matter, she was told her son was exempt because of an intellectual disability.

She was told he would either be put in a grade 2 class or she could keep him at home.

But Ms Thomason says she does not understand why her son cannot be given special help with the NAPLAN test like her other child.

"One of them is getting special help, like getting extra time to complete the test, having somebody supervise them in a smaller group so there's somebody there to ask questions to," she said.

"I don't really know where to go from here. I would like to know where he's sitting, just because he's been diagnosed with a learning disability - we still want to know how he's going."

Ms Thomason says she also does not believe her son has an intellectual disability, even though that is how the school diagnosed him last year.

"I don't think he does but when they did all the tests on him they said he doesn't fit in either box, so they're just going to put him in that box and so he'll get extra help, which is what I'm fine with, but now it's come back to bite us," she said.

'Narrow focus'

Mr Ryan says this kind of behaviour is taking over from quality education.

"There's just such a narrow focus on NAPLAN," he said.

"It's leading to all sorts of unnecessary practices in schools. I have heard of it happening in schools where they've deliberately taken a stance that they don't want below-average students doing the tests and dropping their scores, which probably shows less of an understanding of what the NAPLAN tests are designed to do rather than anything else."

Mr Ryan says schools are also spending too much time grooming students in an attempt to make them perform better in the NAPLAN tests.

"We've got the ridiculous situation of schools just setting aside a whole range of good curriculum offerings just to concentrate on NAPLAN so the school would be seen to be in some way better than the school next to it," he said.

"All these sorts of things, I just find it an abhorrence in terms of good education.

"What we should be doing is concentrating on good education in our schools and we're seeing good curriculum areas being abandoned to simply prepare, test, retest, test again."

Mr Ryan says the pressures education authorities place on schools and teachers encourage them to do the wrong thing.

"That's the disgraceful thing," he said.

"Because it's one test, it's a very minor point of a child's assessment and what we're seeing is a whole reliance on funding, schools being ranked, a whole range of ridiculous things that the test was never designed to do."

Chris Watt from the Independent Education Union says he is unaware of such reports.

Mr Watt says the tests are a diagnostic tool and it would be disappointing to see them used as anything else.

"If there was evidence that a school was suggesting that some students not attend and that others would be encouraged and beyond to be in attendance it would, in our view, be undermining the basis upon which we support the notion of the tests," he said.