What to look for
You want the proper size for your child's back, which makes it vital that the child try on the backpack in the store. Every child is unique, and his or her height and weight determine the choice of backpack. If the bag hangs to the buttocks, keep looking, because it's too big.

The size should also be appropriate for your child's age. Children should never carry a backpack load heavier than 10 percent of their body weight, so a bag for an elementary school student should be no bigger than 40 cm x 27 cm x 14 cm (a capacity of about 20 litres). For high school kids, backpack capacity can range from 30 to 40 litres. To ensure that the backpack is big enough to hold textbooks, bring a few binders or textbooks with you to the store.

Look for wide, padded, anatomically shaped shoulder straps, a padded back and a waist belt. If there's a second strap at chest height, so much the better. Support straps stabilize the bag, providing maximum comfort.

Check that the bag is strong but lightweight. Avoid nylon or plastic backpacks, as they tend to fall apart before the end of the school year. Instead, go for 600-denier polyester because at once lightweight and durable, this has become the norm for quality school backpacks. The denier count won't necessarily appear on the label, so you may have to ask store staff. However, there's no point in shelling out a lot of money for a 1 200-denier polyester or Cordura backpack; these are meant more for hiking.

The seams securing the straps to the bag should be cross-stitched, and zippers should be covered with a flap of material to prevent water penetration. Other useful elements include compartments (very practical for weight distribution), reflective strips, and straps for tightening the fit on either side.

Be wary of backpacks adorned with depictions of the latest popular characters. They generally cost more, often provide less protection for the back and shoulders and are usually made of flimsy material (nylon, plastic or polyester of less than 600 deniers). They're seldom appropriate for daily use, although they're perfect for short weekend visits to a friend's.

Lifespan

The lifespan of a backpack depends on how it's treated but can range from one to five years. Because kids are swayed by fashion and trends, they usually tire of their backpacks before the bags wear out. And short of dragging it through a puddle, a backpack is usually rain and snow resistant. This can be augmented by spraying it with a waterproofing treatment.

Carrying the load

If your child complains of back pain, leans forward or back and/or walks with difficulty, the backpack is either too heavy or doesn't fit properly. It's up to parents to spot this. They should make sure that their child does not overload the backpack and that only essential items go into it.

It is important to teach your child to place the heaviest objects in the centre of the bag, near the body, and then spread the weight by using the compartments for other items. Also, remind your child that a backpack must not be worn slung over one shoulder but over both shoulders and that the waist belt and straps are not there for decoration but to make the bag sit properly on the body. Finally, urge your child to wear the backpack only when necessary, to take it off when on the bus and, once at school, to use a locker.