Do you remember a young one who changed?

I would really appreciate some words of encouragement especially regarding tough children. I was recently substitute teaching with a number of rowdy children who had nearly (maybe zero) self management skills, zero school preparedness. One child could not sit still for even 5 seconds. It was severe. Miraculously she sat still for lunch. So it's in there somewhere. After taking his medicine, another child settled down so he could actually sit still in his chair and do work. But a third child would go around the classroom, slapping kids on the head. And another child would crawl into a classroom backpack shelf. This would happen at the same time. I'm really hoping someone here has a story about a child (or a classroom) who got better over time. Right now I feel blindsighted by numerous (I didn't list everyone's behavior) children in a SMALL class of 13 children. It's hard to believe right at this moment. I hope you have a positive example to share.
For the record: I don't go to church. And I'm wondering if people are too tired or don't have examples.