ST. LOUIS — It's a back-to-school supply that many parents now say, sadly, is a necessity. Bulletproof vests are now available on store shelves in the St. Louis area.

Pedro Beltranena’s 9-year-old daughter, Gabriella, is about to start fourth grade. Along with the typical supplies like pencils, erasers and notebooks, Beltranena’s list had something new this year.

“An armored, bulletproof backpack,” he said.

After the Parkland, Florida shooting, Beltranena felt it was time to take a big step in keeping Gabriella safe.

“The chances of it happening at my daughter's school are very slim. However, just knowing that she has that extra level of protection that's the cost of a dinner for two, for me that's enough peace of mind,” he said.

For around $130, shoppers can pick up the Proshield II backpack at Office Depot Office Max stores. The bag’s maker, Guard Dog Security, claims it will stop many kinds of bullets. So, 5 On Your Side put it to the test

We bought the Proshield II and took it to Tactical (Store) in St. Peters to see what experts think of it. Store manager Alex Milberg said parents interested in this kind of backpack need to read the label carefully.

“Check the rating. That's going to tell you what it's able to stop and then you'll see whether it's actually certified,” said Milberg.

The Proshield II has an official NIJ Level III certification. That’s on par with the kind of light body armor designed to stop handguns that’s worn by police officers around the country.

But does it actually work? We asked Paul Bastean, director of Ultimate Defense Firing Range and Training Center, to help us find out.

First, Bastean fired three rounds from a 9-millimeter pistol. Afterward, he showed us the damage.

“Here's the impact to the front of the bag,” he said. “But nothing penetrated all the way through to the back side.”

Next, he fired a .44 caliber Magnum handgun at the backpack. It damaged the bag, making a large dent in the armor panel. But again, the bullet didn't go through.

“This is gonna hurt, absolutely,” he said, pointing at the dent. “It's gonna leave a big welt and may even break some ribs. But the thing is, it's not as fatal.”

Not even 20 rounds at close range from a fully automatic 9-millimeter submachine gun could bust the backpack.

So, Bastean tried an AR-15 rifle.

“It went all the way through,” he said.

No surprise since the bag isn't designed to stop a rifle. But when we showed the backpack and it’s stopping power to Pedro Beltranena, he said our test made him a believer.

“This is amazing,” he said. “You reinforced my decision to go with this one.”

The teams at Tactical Store and Ultimate Defense Firing Range say you can make a bulletproof bag on your own using a regular backpack and a bulletproof panel. Those run around $80 at both stores.