The State Opposition claims WA schools have lost the equivalent of 342 full-time teachers despite an estimated 11,000 more students entering the State school system this year.
With 287,000 public students forecast to return to school today, Labor says parliamentary estimates hearings have revealed education cuts of $183 million this year.
Shadow education minister Sue Ellery said a reduction in the base number of teacher allocations meant WA schools would not get the 342 full-time equivalent teachers they would have under the previous formula.
"It means bigger class sizes, it means less one-on-one attention for those kids who need a little bit more assistance to stay focused," Ms Ellery said.
Education Department projections in October forecast 287,334 students to be enrolled in State schools in the first semester this year. If accurate, this is an increase of 11,000 students.
Education Minister Peter Collier said actual enrolments would not be known for several weeks.
But he said teacher numbers would remain the same as last year.
"The Opposition is wrong," Mr Collier said. "It's blatantly wrong. I don't know where they got their figures.
"All I can say is the census for the schools still has not been completed and it won't be completed for two to three weeks.
"So there is certainly going to be exactly the same number of teachers.
"Our schools remain the best resourced schools of any other State in the nation, our teachers remain the highest paid teachers in the nation."
Mr Collier said any impact of Budget cuts to education would be "absolutely minimal".
Opposition Leader Mark McGowan accused the minister of engaging in trickery.
"I've never seen an assault on public education like this," he said.
Mr McGowan said 1000 letters from parents, P&Cs and school boards to Mr Collier, which Labor obtained under Freedom of Information laws, showed the WA public felt angry and betrayed by the Government.
Mr Collier confirmed letters had been received but said across the board WA supported its education system better than any other State.