But two incidents in particular made me realise just how misleading the blanket advice "Don't talk to strangers" can be for small children.
In the first, I stopped to ask a little girl who had fallen off a wall if she was all right. In the other I told a little boy to stop throwing stones at the ducklings in the park.
Normal adult behaviour? Not according to my seven-year-old son. In both cases he reprimanded me, saying, "You're a stranger to them, and we've been told not to talk to strangers."
Teacher had spoken and no amount of argument convinced him otherwise. His literal interpretation of such warnings worried me and I asked him to tell me which people he could trust if he was in trouble.
The results were horrifying. We live in a small town and constantly see the same faces. My son identified a couple of dozen people he knew by sight alone as "friendly adults." Strangers to an adult mind; not to him.
We did find one "bad man". A man cycling through an alley way yelled a "thank you!" over his shoulder as I pulled my son out of his way. "He was a stranger and he spoke to us," my son concluded, logically. I despaired.
Since then he has grown older and more sensible and we have had to give him independence, with many warnings.
I say that there are bad people in the world, just as there are children who actually enjoy hurting animals. But there are more good people in the world than bad, just as at school there are more nice children than nasty ones.
The trouble is that it is not possible to tell the difference between good people and bad just by looking. So keeping safe has to mean always being careful, even with people we know, even with bigger children.
Above all, I tell him, trust your instinct. If it feels wrong to you, it probably is wrong. If anything at all worries you, tell mum or dad or a teacher. Don't let anyonetouch your genitals. Don't go inside a friend's house if someone there makes you feel uncomfortable. Setting an example, when with my son I never go close to a car door if drivers ask for directions. I make them shout instead. On the other hand, I tell him not to worry about people who say things like "That's a nice bike" and who walk on.
There is still a whole generation of people who think it normal to make cheerful remarks to children and there is no point getting paranoid about it. Of course I want my son to grow up safe. But I don't want him to grow up thinking that every unknown face is a threat. That is not the way to nurture happy human beings.
This is where teachers could help by nuancing the message. They know their pupils, the area where they live and can judge whether the message has been appropriately understood, by streetwise children and by those from a sheltered background.
Telling children to be careful is a never-ending job. Chanting a simplistic slogan only goes part of the way.
Madeleine McDonald is a parent and a freelance writer.