Do you ask permission of the subjects? A lot of them are close up and I believe you use a 35mm type focal length lens and not a super zoom? Where I live this type of photography might be seen as intrusive. An industrial type area - West of Scotland - rather than a rural area. This why I shoot a lot of political rallies instead. Everyone is fair game and there are always a lot of policemen around which means you don't get hassle unless you point your camera specifically at them. They have their camera teams so my ugly mug is somewhere on their computers.
Stamper, Most of the people in my street photographs have no idea I've made the shot. It's a matter of timing -- something you have to practice and practice in order to get right. In this, the most recent one I'm satisfied with, not one of those kids saw me shoot. Of course it was very dark -- darker than it appears in the picture. Had it been brighter, someone would have seen me and the shot would have been different, possibly even impossible.
My favorite street lens is a 50mm f/1.4 -- on a full-frame camera. Sometimes I'll use a mid-range zoom, but the 50mm forces me to get in close enough that the perspective ends up right. The only time I crop is if I can't get to a point where I can compose what I want in the viewfinder. Lately I sometimes use an Olympus E-P1 with a 17mm lens, which, on the four-thirds sensor comes off as a 34mm equivalent.
The reason I don't ask permission is that a posed picture is very different from the real thing. I might have been able to get those kids to pose for me, but what I'd have ended up with is a picture of a bunch of kids going yah.. yah... yah. What I wanted was the interaction that was going on between the basketball player, the girl on the right edge, and the girl in front with the cigarette. You can't get that in a pose.
But, yes. There are places like your political rallies where street shooting is a joy. I shot this picture on St. George street in St. Augustine, Florida. St. Augustine is a tourist town, and St. George street is a pedestrians-only thoroughfare -- a huge tourist trap loaded with shops and restaurants. Everyone's on vacation and at least half the people on the street are carrying cameras. It's a street-shooter's paradise because no one pays any attention to your camera. I can hang a 24-70mm f/2.8 zoom on my D3, a combination that's huge and menacing, and no one even glances my way. There are other places, like downtown Colorado Springs, where everyone spots your camera right away. That makes life more difficult, but not impossible.