Year 3, 5, 7 and 9 students take the three-day literacy and numeracy exams.
More than one million students across Australia have started this year's round of NAPLAN testing.
NAPLAN ranks a student's literacy and numeracy skills, tracking their progress through their school's curriculum.
At Sydney's Japanese International School, Year 5 students told SBS World News they felt ready for the test and had tried to avoid any stress.
"It was fun, I guess. It's just a bit nervous, we'll see how I went," 10-year-old Annie Lee said after her language conventions test.
"Reading was the easiest for me, because I read a lot of books. But yeah, the language conventions was a little difficult."
Classmate Kotaro Sawai added: "I think I did better than two years ago."
"I just did it like normal, and I think that was my strategy," he said.
Deputy Principal Jodie Hoenig said teachers had worked on boosting student confidence.
"They know that they're capable in regard to NAPLAN," she said.
"They know that bilingualism and a multicultural community offers them a great success."
Ten per cent of Australian schools were meant to begin trialing an online test as part of a three-year roll out. But states and territory leaders rejected the move. NAPLAN will be completely digital from 2019.
"There was a lot of preparation work in the development of the platform," explained Robert Randall, the CEO of the Australian Curriculum and Reporting Authority.
"We will continue our preparation to move online," Mr Randall said.
"This has always been a staged process. We've learnt a lot out of this year, and so the learning that we had through the work that's been done will be applied, and that will make us more confident to take the step in 2018."
While the tests are relatively routine for primary students, there is added pressure for Year 9 pupils in New South Wales and Western Australia.
They need to receive a band eight across the tests to be eligible to sit their final exams in Year 12.
NSW Shadow Education Minister Jihad Dib said the new requirements were too "tough".
"The government has effectively drawn an arbitrary line in the sand assuming that the threat of 'try harder' will be enough in itself to raise academic standards," he said in a statement.
"Students and parents have already come to me, highlighting the negative impact this is having on young people and that there is a very real risk that this policy will backfire."
But Robert Randall said there was no cause for concern.
"For those who don't achieve it, there are no consequences; they will need to continue with their literacy or numeracy," he said.
"They'll work with the authorities in NSW and WA to make sure they get there by the time they're in Year 12. As with NAPLAN in general, people [need to] keep this in context."