That is so true. I am close friends to a family at church, who have the best behaved kids at church (in my opinion, which is slightly baised). However the kids are disciplined and supervised and taught to the point where they don't have much opportunity to be bad. If they disobey me or are disrespectful in front of me and mom's not around, she wants me to let her know asap. Other kids at church whose parents are not as proactive in disciplining and supervising (and believe, it shows) are nowhere near as good.
Now granted, some kids personalities make them seem better than others, but you can definitely tell who's disciplined and supervised to the point of not having a chance to be bad.