1. resisting control or restraint in a difficult manner; unruly.
2. noisy, clamorous, or boisterous: obstreperous children.
What a great word, Obstreperous. Children most often could have this word used to describe them, but it's interesting to me that the two definitions listed have opposite imagery. It also somewhat subjective and depends on one's viewpoint. As the mother of two boys (and then a girl) I am well aware that there have been times others would call my kids obstreperous meaning unruly, while I would only consider them boisterous. (Of course sometimes even I call them unruly and have to reel them back in.)
I'll take the sometimes obstreperous nature of my children and their friends any day - because I believe they will grow up to change the world for the good because of that very nature.