He is being so challenging about absolutely everything at the moment!
As soon as he has to do anything he doesn't want to he is arguing back, back-chatting, resisting and even lying about things.
So e.g. homework sheet to finish, and he'll say "Oh Mr X said we didn't have to finish it if we didn't want to .." (I KNOW this is not true, as I have had an older child go though the same lessons/teacher/school.)
He just WILL NOT accept that I might know anything better than him. He will not be reasoned with...
We have just had a huge row about music practice, as he has an exam in 2 weeks time, and needs to practice. I was asking him to practice certain scales, which are listed in his practice book by his teacher, and he has alreday learnt.
He just kept trying to argue that they weren't going to be in the exam, so he didn't need to practice. 
(I know they are - they are in the book and the syllabus - he is just trying to wriggle out of it all.)
He is acting like a lazy, spolit brat all the time at the moment, and then when he knows that I have 'found him out' about things he gets all tearful and defiant.
Help -I'm at my wits end...
Sometimes I feel like just 'walking away' and letting him fail spectacularly (at his homework/ music exam etc) but that's not really my style of parenting 