What societal norms are important for a child to know?

We home school our children (both 9). When teaching them about St. Patrick’s day we focused on St. Patrick and his relationship with Ireland. We spoke about what is perceived as negative and positive about him, geography, and some history.

We didn’t spend any energy on the color green.

I realized today that my children have no idea that some expect the wearing of green on St. Patty’s day. I have a friend who rolls their eyes at me every time they learn I have omitted certain societal norms from their education. I don’t find many of them worth much energy. Maybe I am missing something.

Are there certain societal norms that seem important to impart?