Fear is the rational reaction to something that can cause harm.

This is true until the "something" become "normal" then there is not fear anymore ... Like the car accidents.

Our children should be aware that there are dangers in the world they live in.

Yes they should! But I do not see it so often lately, at least it does not look like parents are teaching that but the opposite. As @whatsup well says ...

... sometimes feel we live in a society of people who want to remove risk and negative emotions from life instead of live it.

I see this everyday in Germany, where I live.

Edit: What means "The idea that we should keep our schools safe is a good one"? What mean safe?

Edit 2: @whatsup you are a very sensitive "human bicht" ;)