BULLSH1T!!!!! You can't trust teenagers with anything before they've earned that trust - trust is EARNED, not a right.
Teenagers: If you want to talk to your friends, phone them. Better yet, when you're at school, find out what your homework is and don't rely on other, equally scatterbrained, children to tell you. DO YOUR OWN WORK! If you just want to aska simple question, why do you need to MXIT for hours at a time? You're not fooling ME, sunshine...
Parents:Give teenagers NOTHING for free - make them work for whatever they want.
MXIT, Internet, Twitter, and all the rest of that cr@p is just that - CR@P! Teenagers don't need it, deserve it, use it responsibly, or understand anything except "I want, I want, I want"......
When they live under their own roof, paying their own way, then they can do what they want. Until then, they need to EARN their way through behaving responsibly, and behaving maturely.
As for having 'child welfare on speed-dial' - GROW UP! LET them call child welfare. LET them spend the night (or the week) at a "place of safety" - they'll NEVER try that trick again. After a week in one of those places, they'll do ANYTHING to stay at home - they'll willingly give up their cellphones, internet access, the lot. Believe me.
Don't be scared of the little sh1ts - discipline them, and teach them that there are consequences for every single action on their part.
Alternatively, you can give up right now, let them run your home, and do what they like. Why don't you just move into the servant's quarters while you're at it?