We live in the suburbs, about 40 minutes from Manhattan. Up until Newtown last year, the policies were pretty lax. But things have changed.
The policy in my kids' district:
Each time you visit each of the schools you give them your license and it's scanned. The first time, you register, and it's quicker from that point onward. This is new this year, and I love it.
For my Catholic high school: the front door is locked during school hours. Anyone who wants to enter is allowed in-- there's a "porter" whose job is to sign people in and give them a pass.
But the reality is that someone with the intention of doing harm can't be stopped. Someone with a gun can blast through the door and do whatever harm he/she wants. If he or she doesn't have his own safety as a primary concern, then there's nothing to lose.
That reality isn't limited to schools-- it applies to malls and airports and any other place in the world. There's no place on the planet that's "safe." Think back to the scenes of the school shootings since Columbine. For the most part, they weren't in big bad scary cities, they were in places like Newtown Ct, Goddard Kansas, Concord New Hampshire-- places that had always been thought of as "safe."
We used to have good friends-- my kids called them "Aunt and Uncle", we spent endless hours at each other's houses, we babysat each other's kids. He got a job transfer, so they moved to the midwest. Imagine our shock when he was arrested for sexually abusing a minor! And he's not living in some big city; he lives in a small town in the midwest. Nope, he's not legally supposed to be in his son's school, but if no one is checking ID, I'm not sure what would prevent him from being there.
He's been there for a good decade. He's someone's next door neighbor, the one someone waves to every day on the train or bus. He's the onw mowing his lawn and doing such a great job of it. He may be the one your friend finds on match.com, since his wife divorced him after the nightmare. You may see him at church, or at the school car wash.
And if no one runs his ID, he'll be trusted. And he'll have the opportunity to do immeasurable harm to another child.