I'm thinking about our practices.
If they are doing the warm up properly I don't mind if they are chatting. I guess I try to keep things under control rather than come down on them.
You're right that it throws their attention off from what they are doing. The way I handle that is I tell them they did it wrong and they need to do it again. Sometimes I point out one person who was getting it right and ask them to mimick them. This usually works.
Don't forget your dealing with teenage boys with a lack of frontal lobe development. It's amazing they can even come to practice.
It can be frustrating because you see their potential and what they can be if they are giving their all. But as long as they are getting the warmup done enough to prevent injury and strengthen targeted areas then they have done their job.
I understand you can't let everything slide. Sometimes toward the end of the season I let up a bit and get a little bit looser at practice. I have to watch this though. I can remember one day going to practice and I have four different groups warming up in different locations. This just happened overnight. It's not like their was a progression. One group I could not even find during the warm up. When I found them I asked one of the kids where they were? The response was, "Where were we supposed to be?" I actually had to explain they needed to be in the same place they had been for the past three months every single day. This was confusing for them. Again, a lack of brain development can explain some of this.
Sometimes I wonder whether I was this dumb at their age? I'm pretty sure I was. I know my coach liked me and I gave my best but I'm sure In did some things that really annoyed him.
I think the bottom line is that you need to keep the practices light and fun but also make sure they are doing the work.