"I'm not a stranger," I explained.
They relaxed and followed me into the classroom .
Most children are taught not to talk to strangers or go with them, but I wonder how many know just because someone says, "I'm not a stranger" it doesn't mean they aren't.
But they should know it is okay to go with a stranger who is wearing a uniform and helping them in case of an emergency. For example they should let a fireman take them out of a burning building, let a paramedic put them in an ambulance if they're hurt, or get into a police car with an officer who has found them if they were lost.
Older children can understand it is okay to talk to people they don't know when those people are at work doing their jobs. For instance it's okay to talk to a salesclerk in a store, a receptionist in a doctor's office, or a librarian in a library, but they should know not to go with those people if they meet them in other places. Even if they have seen them many times at their jobs, they are still strangers.
And it would be nice if kids understood that it's okay to follow a substitute teacher into their classroom.