Lying

My 12 yr old can't seem to stop lying to his mother lately. I don't know what's happened because he used to be the good one and all of the sudden he's lying about everything, even things he probably wouldn't get in trouble for. Since he's only aloud to watch TV and play video games on Saturday grounding him wasn't very helpful. Taking away the cell phone wasn't helpful either because I make him babysit and sometimes take his little brothers and sister to play at their friends when I can't and he needs his phone for that. He hasn't had an allowance and has been doing extra chores for so long that that isn't a punishment anymore either. I have been driving him to school because it is very embarrassing to be dropped off by your mom when your twelve and that has been a little helpful. I think today I may have found the solution. He wanted to go out and ride bikes with all the other neighborhood kids. Most of them were his age and they came over a few times to ask him to play. At first I said no because he was grounded but that didn't seem like it bothered him much so I decided he could go outside and ride his bike but he couldn't cross the street and every time they asked he had to tell them no because his mommy won't let him cross the street. (I sent Tanner as a spy make sure he told them) He stayed out for about ten minutes before the other kids decided the sidewalk was for babies and they were going off to do something else. I told him if he keeps it up I would be eating lunch with him as well. He swears he will never lye to me again. Lets hope he doesn't because I really don't like school food.