The controversial national literacy and numeracy tests will start on Tuesday, and for the first time students will have no idea which genre of writing they will be asked to do.

More than 1 million students in years 3, 5, 7 and 9 will do NAPLAN tests over the next three days. To try to stop excessive coaching, the Australian Curriculum, Assessment and Reporting Authority is this year keeping the writing section secret so students cannot prepare for it.

In the first tests, students will be asked to write a narrative or a persuasive piece, as well as being tested on spelling, grammar and punctuation. The following days will focus on reading and numeracy skills.

ACARA has repeatedly urged parents not to have their children coached for the tests, arguing it is not a pass or fail exam and excessive preparation does more harm than good. Nevertheless, NAPLAN remains contentious because of the importance some parents and schools place on the exams.

Many private schools ask for primary school NAPLAN results when students enrol in their high schools. As well, parents choose schools for their children based on NAPLAN results published on the federal government's MySchool website. There are also reports of students crying or even vomiting from nerves on test days.

But the chief executive of ACARA, Robert Randall, said this week should be treated like any other on a school's calendar.

Mr Randall said students doing their Year 9 NAPLAN tests this year were the first group to do the inaugural NAPLAN tests in 2008.

“Over this time, parents and teachers of these children have been provided with data and reports that help them place their child’s performance in a school and national context," Mr Randall said.

Results will not be available until later in the year, which frustrates many teachers because they have very little time to work on students' weaknesses.

The Australian Greens spokeswoman for schools, Penny Wright, said NAPLAN tests should be moved to the start of the year to limit “cramming” sessions and relieve pressure on students.

“NAPLAN has become a high-stakes test, where schools are so concerned about MySchool rankings that NAPLAN preparation is taking over the rest of the curriculum," Senator Wright said.

“Holding the tests in term one would also mean the data could get back to teachers and parents early in the year, so there is plenty of time to address any learning gaps.”

Senator Wright said NAPLAN was designed to track students and help them – not to rank schools or to be used as a private school entry test.