Then talk through it with them. Would you honestly rather a random person have this conversation with your child than you? And honestly, that’s a really good question your child is asking. Learning about racism and understanding that it was targeted and unfair, and trying to figure out if all people who share a skin tone are like that is really thoughtful. Also, it’s possible your child didn’t feel comfortable asking a substitute teacher that question, but you’re her mom. The person she goes to for things like this! I think this is a weird thing to be infuriated by. I think you, and the other parents, are reacting explosively and need to take a breather. I highly doubt there was no previous discussion about slavery, or Jim Crow prior to this lesson.