The parents of more than 1400 WA students signed withdrawal forms to stop their children from sitting national reading, writing and maths tests last year, figures show.
School Curriculum and Standards Authority statistics reveal a 23 per cent jump in the proportion of children pulled out of the tests at their parents' request, with 1420 of 121,182 eligible students withdrawn last year compared with 1126 of 118,481 students in 2012.
A few WA schools had withdrawal rates for some classes of between 20 and 100 per cent, compared with national withdrawal rates of between 1.3 per cent for Year 7 and 2.3 per cent for Year 3s.
All students in Years 3, 5, 7 and 9 are expected to complete three days of National Assessment Program Literacy and Numeracy tests unless their parents have filled in a form to say they object on philosophical or religious grounds. Schools are gearing up to start this year's round of tests on Tuesday.
Test participation data on the My School website shows that some schools - mostly alternative private schools - had a high rate of withdrawals.
None of the students from Silver Tree Steiner School in Darlington sat the tests and 97 per cent of Year 3s at Perth Waldorf School were withdrawn.
Spearwood Alternative School, a public school, had a 20 per cent withdrawal rate. Principal Denise Stone said part of the school's ethos was that children develop at different stages and some parents felt that testing each child's progress through NAPLAN was not necessarily consistent with that view.
"In the early days of NAPLAN a number of our parents objected but fewer have withdrawn their children in recent years because we encourage them not to place any greater weighting on the tests than intended," she said.
"Instead, we ask them to see the testing as one small part of a much wider process enabling teachers to see how students are progressing."
Ms Stone said there had been no withdrawals so far this year.
Rob Randall, chief executive of the Australian Curriculum, Assessment and Reporting Authority which manages the tests, said NAPLAN data was used for important decisions about the success of programs and allocation of resources.
"Removing students from the picture can distort the results," he said.