I'm thinking of having the kids jump rope for 150 minutes before they can take a break.
That is way too long. Why would you do that?
It's part of my job to manage the kids' time. I will do what I want with them.
150 minutes of jump roping is too long for a child. They will get tired and it is cruel punishment to make them do this.
It's fine, we only have to do it a couple of times until they learn their lesson. If a kid doesn't learn their lesson at first, my other students will punish them as well, so it's fine.
You shouldn't take advantage of your teaching position to abuse kids. They will get hurt, and their parents will probably have you fired. It will be better for everyone if you're more reasonable.