Sad, but true, I didn’t think much of my 8-year-old daughter’s 15lb. backpack until one day after school when I tossed it into my car and it landed with a massive thud that shook the windows.

That was my “ah-ha" moment.

Since then I’ve done my research and started working with her school and the PTA to get the word out about keeping backpacks – and our kids’ backs – safe during the school year.

In case you don’t already have these tips set to memory – here are a few things you should keep in mind when you’re back-to-school shopping with your kids:

•Look for backpacks with padded, adjustable shoulder straps that, when adjusted, keep the backpack secure against the body.

•The bottom of a well-fitting backpack will rest in the curve of your child’s lower back and will go no lower than four inches below her waist.

•A child should never carry more than 15 percent of her body weight in a backpack – no matter how strong you think she is.

•Load backpacks with the heaviest items to your child’s back – and when possible arrange all the items in the backpack to minimize or avoid shifting.

•Get your child in the habit of wearing both shoulder straps and (if there is one) the waist belt. This will help to keep her from leaning and distribute the bookbag’s weight more evenly.

Of course, getting your kids to actually use both straps – and the belt – and keeping a close eye on the amount of books and other school supplies they keep in their bookbags will be a huge challenge (I know – I’ve been there). But if you can get them to choose the right-size bookbags when you’re back-to-school shopping – and make even a little headway on the other pieces – it will be good step for your kids (and be a huge relief to their young, but aching backs).