Who is to blame for the stress students feels over the annual NAPLAN tests?  The agency in charge is blaming principals and teachers, and they’re pointing fingers right back.

The Australian Curriculum, Assessment and Reporting Authority (ACARA) says student anxiety stems from “poor communications between schools and their communities” leading to false perceptions that NAPLAN is a high-stakes test, and that that principals' and teachers' influence on ''their parent community cannot be understated''.

But Greens school education spokeswoman Penny Wright doesn’t buy that, and she initiated an inquiry that begins in Melbourne on Friday.

“This is really head-in-the-sand stuff from ACARA. I think ACARA is in denial in the face of overwhelming evidence coming into the inquiry,” Senator Wright said.

The Australian Education Union says the standardized tests turned into a “high-stakes environment” and pressure on schools, teachers, students and parents continues to rise.

Separately, the Australian Primary Principals Association warns about use of NAPLAN results to compare schools. It says the student stress, anxiety and illness reported by principals is unacceptable and teachers are also feeling the pressure.

NAPLAN tests the reading, writing, spelling and numeracy skills of year 3, 5, 7 and 9 students.