There's a few things I wish my parents had taught me as a child. Some of it is really basic stuff but has had a massive impact on my life. I don't want my kids to have to go through the same.
Financial - how to budget, loans, mortgages etc
Oral hygiene- my DM had a phobia of the dentist and as a result I only ever went to the dentist twice as a child. She wouldn't let me go.
How to cook
What did you wish your parents told you about.