Here's what you need to know about one of the most controversial school supplies.

This isn't something anyone WANTS to have to think about, but the truth is, sales of bulletproof backpacks have skyrocketed almost 300 percent. Security companies have entered the world of back-to-school products with an array of "ballistic shields": bulletproof and bullet-resistant backpacks and inserts. It's important to understand the rating systems behind the design before making this type of expensive purchase, so I did a bit of digging to bring you the basic information every buyer should know.

Brands

There are several brands on the market right now, including BulletBlocker, Tuffypacks, Guard Dog, and Talos. You can find bags and inserts on their own websites or through third-party retailers. They even have them on Amazon and in mainstream stores like Office Depot.

Courtesy of TuffyPacks, LLC

Ratings

The rating system for ballistic shield backpacks and inserts tells you what caliber of bullet the item will stop. According to the BulletBlocker website, Level IIIA is going to be approximately 8-9 mm thick and can stop higher caliber bullets. It is tested to be effective in stopping 9mm sub-machine gun rounds and .44 magnum rounds. Current news stories, however, are reporting that even that level of protection would not have stopped the bullets used in recent U.S. shootings, based on the types of weapons used.

Cost

Full backpacks range in price from just under $100 to upwards of $500. You can also purchase inserts that can go in any backpack, bag, or purse for about $99-$175, depending on size. For $199, Bulletblocker will create a custom insert for your existing backpack in a custom shape and color.

Courtesy of BulletBlocker

If you're going to make a major purchase like this, do your research and find something that works for your needs. Keep in mind the additional weight and bulk of any item you're considering, and whether it would be overwhelming for the user.

What are your thoughts on the bulletproof backpack trend? Is it a sad reality or a practical security device ... or both? Sound off in the comments.