DS ( nearly 16) is pushing his luck, he cannot keep a civil tongue in his head and it's wearing me out!
I am sick of pulling him up on his manners ( he has beautiful manners ,or so everyone tells me and manages perfectly well to be polite to his dad
) the constant eye rolling,snippines,rudeness and entitlement is driving me slowly bonkers...And EVERYTHING is my fault 
He's a good kid , messing around a bit at school atm and teachers mentioned this at school last week at parents evening. I said if it doesn't improve I would appreciate an email and I will put sanctions in at home- loss of phone,WiFi,grounding etc. I have a feeling his behaviour towards me is because he's pissed off I've found out and his flexing his muscles.
I usually ignore rudenss and general 'Kevin' type behaviour and pick my battles but this needs to stop.
What would you do?
Good points- he's a kind boy, home body usually ,works well at school got nice friends and ( sort of with a push) revising well for gsces,loves sport and is volunteering at a charity shop for work experience so as soon as he's 16 he can apply for retail work.
I have a feeling this is a phase but don't want to be a doormat.
Be kind please as I'm feeling a bit delicate after a particularly trying weekend