Lying was the #1 offense in our house when I was growing up. I still remember at 7 years old, I lied about something to my Dad, and he caught me in the lie ( I don't even remember what I lied about). This was a huge offense in our house, and after explaining to me that people who tell lies cannot be trusted, he and mom banded together, and for a few months, they made a point to double check everything I told them, right in front of me and not trust my word on ANYTHING.
I'll tell you, that made much more of an impression on me than any soap in the mouth or yelling or taking of priviledges would've! I am 31 now, and I still cannot/will not lie to my parents, and I still remember this consequence.
Also, if we were sneaky - almost the same as lying, we wer basically not left unsupervised at all for a long period of time....we had to be around our parents all the time, and whatever we "Snuck" was confiscated for a 2 week period. I would tell him you cannot trust hi mto be home alone, since he cannot follow the rules, and take him with you to take the other kids to violin. Also, check his backpack before he goes to school, for a certain period of time, and like others said, take away the screen time and the iPod, for an decent period of time. Once he proves himself during this time of no screen time and no ipod ( by not lying or sneaking those things or anything else) - and maybe doing some extra chores or something....then he has "earned" them back.
Good Luck....this may seem extreme, but if you make a BIG impression right away, it is less likely to re-occur.
Jessie