Ten Conversation Starters for Parents is a good post from John Spencer. They include some good questions teachers can ask, too.
Here’s one example:
What was the most interesting thing you learned in school today?
As a dad, I want to hear my kids geek out about something cool they learned in school. It might be fractions or volcanoes or some random historical event. Talking about this helps me find informational texts that they might enjoy. It lets me know what they find fascinating that I might be missing at home. Plus, it sets the tone for the fact that learning is still a blast.