I'd put one leader in front with the boys who wanted to be up front, and then another bringing up the rear - usually me. And I told the boys in front that if they ever got out of my sight, then they'd have to join me at the back.

When I was a kid we did a backpacking trip with the scouts - there were probably 20 of us in the Wind Rivers, ages 11 to 17. We got so spread out and some of the boys weren't too keen on the buddy system if their buddy was slowing them down. We ended up losing one kid who was actually right in the middle of the group, but by himself and he kept hiking right beyond the stopping place. Didn't find him until the following morning, about another 2 miles up the trail. His dad was on the trip and was a mess all night, looking for him back along the trail we'd come up. I insisted that we always stay in a group when I was a leader because of that experience.