This is a problem!
Don't know about you, but for years when the boyz came home I asked them about the day. They got used to "Debriefing" me. When they mentioned something counter to !. The facts, 2. Our nation/nationalism, 3. Or was just way out there, I would respond
In "correctable" cases, I would simply email the teacher, correcting them, then check my son the following day to see if the teacher had corrected him/herself. If they did not I wrote a second email cc'ing the principal and school superintendent. Funny, but even today, they all know me by name.