That's not a place to climb. Please get down. Required Please get your backpack, jacket and shoes, and get in the car. The first time. Children have radar that tells them exactly when adults really mean what they say, and when they don't.
Some parents really mean it only after repeatedly ignored requests.
The first time. Your children can learn to believe that when you say it you mean it. Hang in there. It's definitely worth the effort. There is a disease that is rampant among parents.