Around the time he turned six my son my tried to correct my grammar in front of other people (one was a teacher) and I asked him if he was the "grammar police." He told me that would be plural so he was a "grammar cop."

He did figure out really fast that other people don't appreciate pointing out errors, but he still likes to tease me.

I wish we had teachers here like you have at your school, but we don't. They are more like the substitute. Any questioning at all is seen as "talking back."