The shift from elementary to intermediate school was the most traumatic in my opinion.  We were mixed in with older kids from the "Housing".  Smokers and paint sniffers were common.  My niche was heavily sports oriented.  We had good parents but still managed to get into mischief and experimentation.  Although I can reminisce fondly, it was a very difficult time making that transition as the growing pains continued through high school.  Fortunately most of us turned out ok with just a couple of casualties that lost their way permanently during those years and never quite got on track.  It's funny I don't think badly of them but mostly remember the childhood friendships of the elementary years that bonded us.