Prime Minister Malcolm Turnbull has called for maths and science to be made compulsory for all students finishing high school to arrest a steep decline in Australia's standards across both subject areas.

Speaking in western Sydney on Sunday, Mr Turnbull said the push was a "big priority" for the government, after a similar proposal from former education minister Christopher Pyne was rejected by the states last year.

"In my generation, you had to do maths or science to complete high school. Many parts of Australia now, you don't have to do that," said Mr Turnbull.