Avrom > halachos that say if your fellow is sinning, you should just watch and see how it goes for him.
fair correction that I generalized your statement too far. On this point, we have a notion that those who should give tochacha should, but those who do not know how to do it properly should abstain. Of course, parents do not have the luxury… I am not saying though to totally abstain, just to consider what are real consequences of the information you provide. Of course, in many cases, it is the right thing to report, I am just suggesting full consideration. Say, parents are abusive – will you still report thing to them?