There are several things that could have been done to make each classroom more secure though.
Have solid core doors and a good lock and bolt to close off the classroom from the inside. If there is a glass window on the door, mount a flap on it that can be closed while locking the door. Make any glass in the door wired security glass.
Several precautions could have been taken.
This is Connecticut.
Even Virginia failed to address the physical problems and that would take a separate and very costly lawsuit, but there were some whoppers. That's one of the reasons that particular building is no longer used for classrooms.
So, let's start with the problems ~ in CT
(1) failure to use a full courtyard design so that all entry and exit can be controlled.
(2) failure to use bullet proof materials on the exterior ~ to wit, windows were exposed to uncontrolled external environment and were not bullet proof.
(3) failure to make school attendance laws voluntary so the burden of being on the premises fell back on the parents rather than the local school district.
(4) failure to have capable armed personnel on the premises prepared to repel an attack of this nature.
(5) and, most likely, door exit locking systems that are easily frustrated with a simple chain (something to be checked out of course).
Returning to VA a moment, others thinking about these aspects of the situation might turn their attention to wire reinforced glass ~ which KEPT THE COPS OUT OF THE BUILDING at Virginia Tech! They are good for deterring casual theft, but become part of the killing machine when dealing with a nut case!
Or, they’ll just set up a fund for the taxpayers to “invest” in. The could have a Cabinet-level Department to waste money on such things.
“Barring bullet-proof bubble-wrap, there is just no way to ensure 100% safety and security.”
Within twenty years, expect to see new schools constructed along the lines of prisons, or perhaps more likely the Nazi concentration camps (with high builds of barbed-wire fence around the perimeters, rather than outright walls).
All gates will be manned by security officers, probably toting “assault” rifles.
In the name of safety and security, of course .