How to control a kid?

Nowadays children are getting more difficult to teach and to guide. What's happening to them? Is it because they are expose to our current environment, perhaps children are too clever or parents are giving them too much of freedom to express their feeling. Do we need to use a rod while teaching them? On my point of view, sometimes to certain extent, when children get to naughty or rebellious, we need to use rod. This is to let them know the consequences of doing a bad action. What do you think?