(NewsNation) — Bulletproof backpacks proved to be ineffective against AR-15 rifle rounds, a NewsNation investigation showed, but even bullets from lower-caliber weapons fired at the backpacks can lead to severe injury.

NewsNation spoke with surgeon Rodrigo Gerardo about what could happen to a child if a lower-caliber weapon were fired at a bulletproof backpack. Based on how the backpack bends and folds while catching the bullet, Gerardo said the child end up with “significant” damage to their organs.

“It could be deadly, it could cause a significant injury to their spine, and that can sometimes lead to paralysis,” Gerardo said. “Or, there are a lot of important organs in the back, so if this is hitting a child in the back, it could be equivalent to hitting them in the back with a baseball bat.”

Demand for bulletproof backpacks has continued to rise in the wake of mass shooting inside U.S. schools. In light of that, NewsNation set out to test the effectiveness of them.

Guard Dog Security, purveyor of one of the most widely available bulletproof backpacks, let NewsNation test different caliber bullets on their bags. The conclusion: It would take six inches of textbooks and the backpack to stop the bullet from an AR-15-style rifle.