I've stayed at Clarksburg State Park with my young son for a few years in a row and have always been consistently impressed with how clean and peaceful it is.  Maybe we've just gotten lucky, but each time we've stayed, no matter how busy the campground is, it's quiet, especially at night.  The park and the campground feel quite secluded for the location - very close to North Adams and other towns in that part of the Berkshires.  The pond and the hiking trail around it are beautiful.  We'll definitely return!  My only complaint is that Massachusetts charges out-of-state residents 3x as much to camp.