Many schools have thousands of children, teachers and staff who could take hours to funnel in and out of a single entrance every day. Even more use portable buildings or have multiple buildings, with children and staff often moving among them. Not to mention that renovations to older schools, which officials say typically have more exterior entrances, put a heavy burden on local taxpayers.

“It is not feasible to think we’re going to ever get to the point where we have one door in and one door out,” said Bill Avera, chief of police and emergency manager for the Jacksonville Independent School District in East Texas and a board member of the Texas School Safety Center…

“Let’s say you had a high school that had 3,000 students, and you’re going to use one entry point to bring those students into that building every day,” Avera said. “That’s going to literally double the amount of time it takes to get folks in that building.”

Schools also have to account for staff and deliveries for things like lunch items and classroom materials, Avera said.