Find their level and speak to em at that - rewards for good stuff - be unmoving for others. They will play you -play them back
Always explain your reasons for good or bad. Make them think - turn it around. Give them options. Then they choose thier punishment or otherwise.
Adolecents - know it all - know feck all - we know that - they dont!
I've got 2 of the ******s - however mine are nice - but it doens't mean ihaven't had to be devious in the past