Insiders say there is a massive disparity between the fees charged to WA public high school students studying trade subjects.

High school students need an Australian Tertiary Admission Rank (ATAR) or a Certificate II in vocational training to complete Year 12 and get a WA Certificate of Education (WACE).

The State School Teachers Union WA (SSTUWA) says those students who choose Certificate II streams are being left thousands of dollars out of pocket at some schools, while others receive the courses for free.

WA Education Minister recently tabled figures showing that Australind Senior High School charges $3,320 to get a Certificate II in plumbing, but just one suburb over at Eaton Community College, it is offered for free.

Public schools use private Registered Training Organisations (RTO) to deliver the courses, and the Department of Education says schools determine how much of the cost it will pass on to parents.

Funding is decided based on Year 9 assessments, which are used to sort students into either ATAR or vocational streams.

“If a school wants to offer both options to a student the school is the one who has to pay for it,” said SSTUWA vice president Samantha Schofield.

“Schools are under very difficult financial pressures where they're having to make decisions about subjects based on funding and not necessarily the needs of the students themselves.”

The Council of State School Organisations WA wants equity for students no matter where they study.