Why aren't schools locked down all the time?

They are talking on the news about how the schools in the district in CT have gone to lockdown following the shooting. Isn't that like closing the barn door after the horse runs off?

Wouldn't the schools be safer if they were locked all the time?

As a parent I would have no problem having to stop in a lobby or anteroom and speak to someone behind one of those security windows before being buzzed into the main building. A little determent could have saved a lot of lives today.

I'm going to speak with my Congressman and Superintendent of Schools. Maybe you should do the same.

Food for thought.

• Connecticut school shooting