And yes, that leads exactly where you expect it would.
Because you're listed as a substitute teacher, and you've been a guest lecturer, at the public and private school, they can use you immediately, while the other options they're pursuing have to go through paperwork and background checks, so you agree to help out for at least the rest of the week.
You're mostly working with the middle school kids (7th and 8th grade - 12 and 13 year olds mostly). Among those boys are several who are friends of your boys, and to whom you're close. You talk to them privately before practice starts and warn them that you're Coach, not Uncle for the duration of practice.
They accept that just fine, and they help you set the tone of serious, hard work, but also working towards goals and looking for a bit of fun.
Unfortunately, one of the boys takes that last part a bit far.
Since you're mostly a soccer coach, you're starting with heavy drilling. As you're looking around, you see one boy, Ricky
The boys get water breaks every fifteen minutes, because of the hot weather, and you give the other boys theirs. When you confront Ricky, he doesn't have time to come up with a good story and ends up admitting what happened. You let him get his water break, then you put him on wind sprints while the other boys start passing/receiving drills (definitely more fun).
Once you have them started, you look back at Ricky, and he's gone again. A quick scan reveals he's decided to take another water break (maybe five minutes has passed, certainly not more than that).
You go over to him and instruct him to go to the locker room, shower, and dress. He's done for the day, and he'll need to talk to the head coach to see if he's still on the team. He gets upset, but you explain that this is voluntary, and you really don't feel like fighting with someone who doesn't want to participate. He whines a bit more, but finally leaves.
Day and night pass, and the next morning (this morning), you're called into the principal's office. Ricky is there, along with his father.
Before you even have a chance to brace for a fight, Ricky and his father both apologize to you. The father then explains that they talked to the head coach, but both the head coach and principal said it was your decision, so you had to reverse it. Ricky's father also informs you that he had a long talk with Ricky to inform him that team sports require maximum effort from everyone. Ricky had just been playing around and hadn't meant to cause trouble, but he hadn't realized how he was hurting the entire time.
On the other hand, Ricky's Dad continues, he had deliberately disobeyed his instructor, and after the long talk, Ricky had gotten a 'good whupping'.
After all this is summed up, Ricky says (obviously at his father's prodding), that he knows he screwed up, and that if you reverse this punishment, he'll deserve something else. The principal says it's up to you and he'll support or administer whatever you think fair.
What's fair to Ricky, to you, and to the whole team?