Despite advances in classroom technology, the weight of school backpacks continues to grow, with experts advising parents to look for physical signs that it's affecting their children.

Nicole Haynes, chair of the Australian Physiotherapy Association's paediatric physiotherapy group, said parents should look for physical signs that it's affecting their children.

"From a physical perspective, if they're having to really lean forward to hold their backpack and bend at the waist, then that's the biggest physical sign you can see," she said.

"We want to make sure kids are independent with carrying their backpacks and encouraging them to be active at the same time."

She said in early primary school years, students often had bags that were too big for them.