$ 10.7 billion.

It's no small amount, but it would add up to a very worthy investment.

After all, a rough assessment suggests that’s what it would cost to secure our K-12 public schools and secondary education facilities. That $10.7 billion number represents two armed security guards being assigned to every public education institution in the nation.

I calculate $10.7 billion based on government statistics which estimate the total number of K-12 public schools at around 99,000 and post-secondary education facilities at around 8,000. That gives 107,000 total. Multiply 107,000 by 100,000 (two security guards each making $50,000 a year) and you get $10.7 billion. I believe $50,000 is a good total estimate for the average security guard salary when taking into account state-level variations in average wage.

Why two guards and not one?

Because with two trained, armed guards in every school, there would be strength in numbers with which to respond to a shooting incident. It is worth noting here, however, that there was one armed guard at the Parkland high school targeted in yesterday's shooting. To be clear, while armed guards have prevented atrocities, they are not an elixir that will solve the issue entirely.

I simply believe they can help.

It's not just about the ability to dominate an attacker in the earliest moments of his or her attempted atrocity. It's that security officers could identify the sound or other signs of gunshots more easily than students or staff, thus enabling a quicker police response. They could also position themselves near to the various entry points of a school, preventing the kind of attack that we saw yesterday.

To be sure, it’s not a perfect solution. A gunman could still kill students before being isolated and neutralized.

Yet I don't believe the cost consideration is relevant here. There are plenty of areas in the federal budget where we could find money. We could, for example, start by privatizing airport screening services. Nor do I believe that armed guards would intimidate students. Millions of American families own guns in their homes and everyone is used to seeing armed police officers out and about every day.

Moreover, the key question in relation to school safety is a simple one: how best can we protect students and staff as they go about the moral endeavor of learning?

The answer to that question is not going to be found in reflexive bans on guns or tweets about mental health. The best answer is to provide security at the final point of threat: the schools themselves. $10.7 billion is a small price to pay so that students can focus on history, math, literature and science, and not on the prospective threat of mass murder.

Note: this piece has been updated to reflect the fact that an armed guard was present at Parkland's Stoneman Douglas High School during the February 14th shooting incident.