However, parents shouldn’t be afraid of their child carrying some weight in their bag.

Research has shown that wearing school bags might actually help to prevent back pain in adolescence.

“Back packs — even reasonably heavy ones — don’t necessarily damage backs,” physiotherapist and research fellow Adrian Traeger said.

“Parents shouldn't be worried about their children carrying some load in their bag. Excessively weighty bags — where the child is clearly uncomfortable — are not advisable.

“But carrying some load to and from school is perfectly safe and probably useful in the long run.”

APA physiotherapists recommend aiming for comfort with a backpack, and talking to your child about whether they feel their bag is too heavy or too light. The association recommended that children use both shoulder straps and place heavier items closer to the body. 

“A comfortable back pack is a key part of creating a physical activity routine that your child will stick to,” Mr Traeger said.

“There is no good evidence that wearing back packs adversely affects a child's health—but there is good evidence that physical inactivity does.”

The physical activity guidelines for children of primary school age in Australia recommend at least an hour of moderate to vigorous physical activity each day. This should be combined with strengthening or weight-bearing activity three times each week.