"I would ask this question: If you need a bulletproof backpack, wouldn't the child also need a bulletproof front pack and a helmet and a Captain America shield?"
He noted that children often don't have their backpacks nearby when they're in school.
More from NBC News:
20-year-old charged after school shooting
Arizona sheriff: Armed militias beware or be shot
Spending to fight raging wildfires tops $1 billion
"I have a vision of a classroom of kids running down a gym court playing basketball with their backpacks on," he said. "And the ballistic whiteboard? Is the teacher going to tell 25 kids to line up behind at the right angle?"
Michael Dorn, executive director of Safe Havens International, a non-profit that has conducted more than 5,000 school safety assessments, said his group has been bombarded with armored product pitches.
One German engineering firm even offered to make an entire school bullet-resistant—at a cost of more than $3 million.
The problem with these inventions is "they're not practical from a cost-benefit standpoint," Dorn said.
"We could cut the death rate in half in our schools with things like good student supervision and better drill processes."
(Read more: 1 in 4 of all grads are ready for life)
Still, with memories of the bloodshed at Virginia Tech, Sandy Hook, and other schools still fresh, administrators and parents are shelling out big bucks to give their students any edge on surviving a mass shooting.
"We've been selling them all over the United States," Steve Jurak of the San Diego firm Mighty Mojo said of the LifePlate, a $149.95 backpack insert that he says can stop a bullet from a .44 Magnum fired at 15 feet.
"Whenever there is a blip, some random act of violence, we see a surge in sales."
The University of Maryland Eastern Shore just spent almost $60,000 from a private foundation to buy 200 bulletproof whiteboards—at $299 each—from the military vendor Hardwire.
"I heard a faculty member who had worked at Virginia Tech say yesterday that if investing $50,000 saves one life, it's worth it," college spokesman Bill Robinson said. "We understand it's not the panacea, but it's a tool in the toolbox of security."
Hardwire chief executive George Tunis said the 18-inch whiteboards, which weigh less than a pound, can be positioned near classroom doors so a teacher can grab one to defend against an intruder—or even use it to whack a gunman.
"It doesn't replace locking the door but in the event that we're breached at least I have something I can go after them with," Tunis said.
School districts in Minnesota and North Dakota and individual private and public schools have signed on, he said. Thousands of parents have purchased Hardwire's $99 bag inserts. The company even offers a bulletproof classroom door cover for $1,499.