There are fears Aboriginal students will be worst affected by education budget cuts.
The loss of Indigenous teacher aides is causing concern in the state's north.
The Education Minister last month announced 500 education jobs would be axed across the state.
Of that total, the positions of 350 teacher aides will go.
Some of them are Indigenous teacher aides who, in the Kimberley, assist students who struggle with English and are among the worst performing students in country.
The State School Teachers Union's Pat Byrne says it is a terrible way to try to save money.
"These people perform a significant role in schools with a high Indigenous population," she said.
The Education Department's district director Greg Robson says the impact in the classroom will be minimal.
"There'll be a reduction in support but that doesn't mean that support vanishes," he said.
Teachers in remote Aboriginal communities across the north-west are planning to go on strike tomorrow.