How can schools improve their intruder protocol?

My children’s  schools never had a schedule on the outside door of the classroom. I have never seen a schedule of when the room is in use posted in any school.

The classroom door needs to be able to be locked from the inside. There are gadgets for classroom doors the teacher can easily slip in the door handle then the intruder can not open the door.  

A dark quite classroom is hopefully over looked and passed by. 

Our high school has doors that can be closed to block entrance to hallways. This can prevent an intruder (or fire) from going into another section of the school.  These doors are locked when there are inside sport games or plays or concerts going on. Student and guests can come in but only have access to part of the school. 

In our whole school district school  doors leading outside are locked. Anyone can get out, but no one can get in.  Guests must enter through the front entrance after school starts. A office staff member needs to buzz them in.  Our HS and middle school have two sets of doors at the main entrance. Once buzzed in a guest can only get into the main office. The other set of doors are locked.  

Some schools have ID landyard that are worn by all staff and students. ANYONE without a ID hanging from their neck will be stopped.   This is done also to stop any student from another school from mixing in.  

That's not true in every school building nationwide. Only some of them have schedules on the doors. My high school didn't have anything like that when I was growing up.

Well it seems like an easy fix for this issue is to remove that schedule from outside the door.  However, most school classrooms are occupied for most parts of the day, so someone could assume with good odds that students are in any given classroom. 

School intruders are certainly a concern, but they are not common.  Schools have developed strong security plans in the last decade; they certainly aren't foolproof, but they are much better than in the past.

You realize that your chances of being injured by an intruder at your school are microscopic. You're more likely to be struck by lightening. You're MUCH more likely to be injured in a car accident. Why don't you try worrying about the things that are really a threat to you, and working out solutions for it? 

My suggestion is to pass a law that says anyone who trespasses on school property must be a first grade teacher for a week.  I’m betting people won’t come within five hundred yards of any school.