The Cancer Council's National Secondary Students' Diet and Activity study found that only 16 per cent of Australian secondary school students were fitting in 60 minutes of physical activity each day.

Boys were twice as likely as girls to meet the recommended guidelines, the Cancer Council said.

Cancer Council nutrition and physical activity committee chair Clare Hughes said the drop in physical activity could be traced, in part, to the school.

"When we look at the combined cohort, over half [of the respondents] said a lack of physical activity options in school was a barrier," she said.

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AEU Tasmania branch president David Genford said that the union had seen physical activity in schools "maintained at a consistent level", but also noted that educators "no longer have the capacity to coordinate lunch-time or after-school organised sport that was previously offered".

"It is disappointing to see research indicating a large portion of Australian students aren't meeting the minimum recommended levels of exercise, and the AEU would advocate for better resourcing in schools to allow students to meet these minimum recommended levels," Mr Genford said.

"Teachers in schools are continually being asked to do more and more, without the time to do it.

"Additional funding is needed to run programs that will encourage students to be active both during and after school hours.

"Our governments must commit to fully funding schools to the minimum Schooling Resource Standard to give students the best chance at achieving classroom success and maintaining good health."

State Education Minister Sarah Courtney said a strong focus on physical activity among young people was "critical".

"As the new Minister for Education I'm committed to maintaining a strong emphasis [on physical activity] within our education system," she said.

"In our schools, students are supported to make decisions about their health, wellbeing [and] safety and participate in physical activity through the Australian Curriculum in Health and Physical Education.

"In addition, the Wellbeing and the Environment Action Plan highlights the important elements that contribute to physical wellbeing and addresses them in key actions that focus on physical activity, nutrition and the environment."