There are around 27,000 high schools in the United States. The metal detectors used at airports cost around 4,200 dollars each. Most schools have multiple entrances with a lot of people, so you would need a lot of metal detectors to keep traffic flowing smoothly. So let's suppose there are 6 metal detectors at the front entrance of a school (I mean the shooter could just go through other doors but meh). 4200 x 6 = 25,200 Now we multiply 25,200 (the cost for one high school) by 27,000 (the number of high schools in the US) and we get a total of 680,400,000 dollars. Then you have to pay for the training of all of the people who work the stations, pay said security guards, pay the people who will install them, pay the people to maintain them. This is only high schools too. Where I live, there are 6 elementary schools that feed into 2 middle schools, and that goes to one high school. That will also add to the already high cost. Yes, I get that the children's lives are much more important than the financial costs, but there is a much more cost-effective way to protect the schools, and it doesn't involve turning it into a maximum security prison. In 2016, there were around 40,000 homeless veterans and 453,000 unemployed veterans. If we took veterans who were mentally healthy, trained them to protect schools, we could create a huge number of new jobs, give veterans a stable income, protect America's youth, and not significantly alter the budget. If 100% of unemployed veterans were able-bodied to do this, we could give schools an average of 16 more security guards. This will make a potential shooter think twice, seeing as he is now not shooting completely unopposed (our high school has one or two on a regular basis). Just my two cents.