Five years of gains at schools are at risk of stalling after the latest national literacy and numeracy tests showed WA students' results plateaued this year.
Education Minister Peter Collier said WA was the most improved State since the National Assessment Program Literacy and Numeracy tests began in 2008 but this year's results showed little progress, if any, since last year.
Children in Years 3, 5, 7 and 9 from all schools sat the tests in May to assess skills in reading, writing persuasively, spelling, punctuation and grammar, and maths.
In 15 of the 20 categories, WA students' scores were steady compared with last year, which was the State's best. There was significant improvement in Year 5 spelling and Year 7 grammar and punctuation, but scores went backwards in Year 5 grammar and punctuation and Year 7 writing and numeracy.
For the percentage of children achieving minimum national standards, WA was above average in four of the 20 assessments, one more than in 2011. Year 7 students met or exceeded the benchmarks in writing and numeracy, as did Year 9 students in writing and spelling.
The Year 7 writing performance was the second best in the country.
Despite the good result in Year 9, the lowest number of WA students met the national benchmark for writing compared with other States (82.7 per cent).
The highest number of students to reach a national benchmark was in Year 7 grammar and punctuation at 94.8 per cent.
Mr Collier defended this year's results, saying WA students had consolidated recent gains and there was evidence the Government's focus on literacy and numeracy in early school years was paying off.
"The report shows that of the 16 assessments that can be compared from 2008, WA students have improved significantly in 11 of the testing areas during this time," Mr Collier said.
"There are no notable declines in the remaining five assessment areas. The continuation of these trends in student performance is encouraging."
Federal School Education Minister Peter Garrett said about 92 per cent of the one million children who sat the tests met the minimum standards but more work was needed to achieve the Government's new goal of having Australia in the top five education systems by 2025.
Federal shadow education minister Christopher Pyne said despite a 44 per cent increase in school funding in the past decade, results had plateaued and more attention was needed on lifting teacher quality, giving principals more autonomy and creating a robust curriculum.
Parents will be posted their child's NAPLAN results from Monday. Individual school results will be published on MySchool website early next year.