By John McDevitt

PHILADELPHIA (CBS) - You see bullet resistant glass in places like banks and government buildings, but not too many schools have them. There is a big reason why.

The bullet resistant glass is expensive — up to $60 a square foot — according to Tom Briggs, president of U.S. Armor. “And of course you got the framing and the installation.”

His Massachusetts company supplies glass to installers across the country including here in Philadelphia.

“We make it to withstand whatever the customer is looking for anywhere from 9mm to .50 caliber.”

Briggs says he has had school customers prior to this month and the schools “limited the bullet resent glass to one section of the school because of the high cost.”

“And we just did all the glass in the cafeteria.”

Briggs did not say if any schools from our region asked for price quotes but did say there have been some inquires since the Sandy Hook Elementary shooting massacre.