Best parenting lesson

I am always told that my children is so polite, that they say please and thank you and treat their friends parents with respect!

This is something I have taught them from small as my mother taught me, always to respect your elders!

I have just one question; why is it that I hear what a wonderful help my teenage son is when he is visiting friends and yet at home his room looks as if a Hurricane just went though it?
 
Delanie