Is it ever okay to discipline somebody else’s child?

As a stay-at-home-mom I have the “privilege” of watching my kids ALL THE TIME! I get to see who they interact with and how they interact. I get to know their friends and frenemies and often times, I end up acting as a parent to both. Which is why I often find myself in situations where I have to discipline other people’s kids. Is it ever acceptable? I think so, here’s why…