With regards to "spare the rod, spoil the child", I think we have to remember that the "rod" isn't necessarily physical. There are many other very effective ways to reenforce boundaries aside from a swat on the behind. (Not that a swat on the behind isnt sometimes necessary as an attention grabber). What I often see in families with difficult or unruly children are a series of mixed messages, or inconsistencies in what is expected, what is reinforced and how it is reenforced. For example, I've taught many kids who must go to bed early because their marks are falling, yet an unsupervised television and video game console sits on top of the "study desk" in their bedroom giving the kid full access any time day or night. Kids are also often set up to fail because they are inappropriately 'punished' for their transgressions, or the punishment doesn't fit the crime. There is no mechanism to correct the behavior. For example, suspending a student for skipping school is ludicrous when you think about it.
When I think back on it, it's an awful lot like training horses. We know that with horses, the correction must be appropriate to the offense and that consistency is everything. Just as inconsistency is unfair to the horse who is expected to learn it is also unfair to the kid who is expected to learn. Being diligent in correcting and guiding even the smallest behaviors is hard work and requires us to see above ourselves in concern for the other person, or animal. So often with both kids and horses, we respond emotionally to poor behavior, which usually goes hand in hand with applying inconsistent or inappropriate "punishments" rather than corrections. In my mind, punishment says, " I care about how your behavior affects me", where a correction says, "I care about how your behavior affects you". Those people who successfully work with kids and parent kids to become great people and those that successfully train horses know the difference well. I guess that is what makes them good leaders.