Just based on my experience, kids who were riding within talking distance (like 20-30 yard at most) of their parents are better controlled than kids who were 100 yards away. The reason is when a parent sees me ride pass them, the parents will ask their kids to stay on the right side or ask them to watch for me and ALL of them have able to avoid me or not freak out when I approach them. Kids who were 100 yards or so...well, they freak out because they didn't know what was coming behind him/her (saying "behind you or on your left" doesn't work) and they tend to ride carelessly (like zig-zagging, do an instant u-turn without looking first, etc.) and ends up me braking hard to avoid hitting them. Finally I find it especially ignored when a kid has not able to fully control their bikes (basically when they're still trying to learn to ride) yet and these "parents of the year" still allow them to ride 100 yards ahead. One of these days, I'm going to have a parent scream at me (from 100 yards away) about how I should watch where I'm riding when I have a near-miss with their kid. Again, that's based on my experience and not generalizing in any way.