The latest Programme for International Student Assessment (PISA) results reveal Australian children dropped nine points in maths and seven in reading, while science improved by two points.
All scores were above the OECD average.
It continues a downward trend across the country since the early 2000s - results down 46 points in maths, 37 points in reading and 18 points in science.
Opposition education spokesman Julian Leeser said the number of topics being taught in classrooms should be streamlined in order to boost results.
"We don't need keyhole surgery, we need open heart surgery," he told reporters in Canberra on Wednesday,
"That starts with removing the cross-curricular priorities. How can you properly teach subjects if you've got these cross-curricular priorities, which are making the curriculum overcrowded and confused?"
The opposition says stronger discipline in schools, including on uniform standards, will translate into better academic results.
"Kids cannot learn if there's no discipline in the classrooms and if the classrooms are not there regularly," Mr Leeser said.
"If you can't enforce something as basic as uniform standards, how can you enforce classroom discipline and ensure that students get to work?"
Australian Education Union federal president Correna Haythorpe also pointed to growing challenges that teachers must manage.
''Teachers are dealing with increasing complexity in classrooms, with growth in inequity and students with diverse needs requiring additional supports,'' she said.
Greens education spokeswoman Penny Allman-Payne said more support was needed for teachers if results were to be improved.
"Blaming teachers and kids is not going to end classroom disruption," she said.
"Kids aren't acting up for the hell of it. They're disruptive because they're disengaged, and they're disengaged because teachers aren't empowered and supported to ensure learning works for every student."
Education Minister Jason Clare said Australia was implementing measures to improve performances, pointing to steps the UK had taken that had boosted their results.
"Reform is hard and it takes time to shift the needle, but it's not impossible. That's what the UK results show and what the agreements we have signed with every state and territory are all about," he said.
"This year we rolled out a year 1 phonics check across all Australian public schools for the first time.
''We are going to do the same thing with maths, a year 1 numeracy check to identify kids who are behind when they are little and make sure they get additional help.''
13°C