Preparing for national reading, writing and maths tests fails to improve literacy and numeracy but takes time from important subjects such as music and sport, a survey of teachers reveals.
They say the work also makes for boring lessons.
Murdoch University education researcher Greg Thompson is one month into a three-month survey of WA and South Australian teachers on the effects of the annual National Assessment Program - Literacy and Numeracy regime on schools.
Students in Years 3, 5, 7 and 9 will sit this year's tests in two weeks.
Dr Thompson said a preliminary analysis of the 600 responses so far showed teacher were concerned that many schools spent most of first term and the first few weeks of the second preparing students for NAPLAN.
"The response from teachers would seem to indicate they really are concerned that the curriculum is being narrowed in order to focus on the tests," he said.
Despite all the time spent, many teachers were concerned this did not make a significant difference to literacy and numeracy.
"Teachers generally haven't found that NAPLAN has improved the literacy and numeracy of their students," he said.
Dr Thompson said international research showed a key indicator for literacy and numeracy success was studying a broad range of subjects such as music, drama and physical education. "If they are being squeezed out in order to focus on this, it's going to have probably the opposite effect of what's intended," he said.
Dr Thompson said many teachers believed they had to adopt a lecturing mode to prepare for NAPLAN instead of encouraging discovery-based learning.
"The argument that has come through is this has not resulted in classrooms that are either inspiring or motivating," he said.
The data also showed that NAPLAN added to teachers' administrative load. But only about half reported being stressed over the fear that poor test results could affect their career.
Dr Thompson said he would present preliminary findings at a principals' conference next month and a final report on the survey would be released in September.