I am really struggling with my 6.5 year old son - he can be lovely, but can also be really hard work... this takes the form of - if he does something wrong/naughty like throwing a piece of lego at his 3 year old brother, or deliberately tripping his brother up - and then he is picked up on this, he denies all knowledge that he has done anything, answers back etc etc. Tonight he was becoming v stroppy - when I warned him that if he threw something else at his brother then he wouldn't get his usual bedtime story - and he then did it again - he went beserk - throwing things at me, lashing out, weeping, shouting - you name it - he did it! He is very tired tonight - but that's no excuse. I can't seem to get past the fact that he won't even admit or acknowledge that he has done something that he shouldn't have - so all talk of "consequences" is very hard. Any tips on how to try to break the cycle would be much appreciated... am feeling slightly at the end of my tether 
. (some background: not all behaviour is directed at his brother but a lot, hubby works away from home in the week so I am working mum on my own most school nights, we are soon to move house which our kids don't know yet as we haven't exchanged contracts yet, but ds1 likely to be picking up on vibes)