When kids become teenagers they need to test new behaviors to see what is acceptable and what is not. While you as a parent try to direct and instruct, most of it does not sink in anyway, so you should learn to overlook certain less important things they do that would normally be considered wrong, but are relatively harmless. I would not tolerate lying at all about anything. The cereal bars...she probably thinks she is getting away with something, and what's the harm in that? Buy an extra box and don't tell her it's ok, just let her take them.

You've heard the phrase "pick your battles"? Now is the time to apply that. Lay down the major rules and leave no room to compromise on them. But for smaller things that won't matter in a year, pretend ignorance sometimes.

This is just my opinion. But I will say that too many rules, lectures and punishments are not good. Kids and teens should be having fun, not worrying all the time about getting punished.