Why does my son always lie to me?

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he is 10 years old and thinks that he can get away with everything..He constantly lies to me about anything...even after I pick him up from school..we are in front of his classroom and I ask him..do you have your homework..he always tells me yeah...we get home and he misses two/three pages..and ends up getting detention at school the next day...Thats not all..he looks me straight in the eye and lies.. Why does he think i dont know..I am his mom with physic reads..lol...no,really..I am really frustrated with my boy...he cant tell the truth about anything anymore..and always blames his sisters for everything...I took away the video games,tv,toys..it doesn't help... What should i do????????HELP