Do you have a handbook NT? if so, discipline is definitely a page you need to add.
Here's a copy and paste of mine.
The Kids
We hope you?ll become good friends with the boys,?however it is very important that you make it clear from the start that you are an adult and in charge.
It will take bit of time for them to accept you fully but it will help if you?.
Treat them with respect and ask for the same?.
Do not make promises you can?t or won?t keep
Talk to them and listen to their answer.
Be consistent
Deal with sticky behaviour quickly and with humour?ie..if they don?t want to get dressed in the morning,?turn it into a game or a race
Unacceptable Behaviour
The boys are generally well behaved however incidents can happen when they are tired / fed up
Please use your common sense but includes:
Fighting
Pushing
Hitting
Not doing as they are told
Rude or cheeky behaviour
Please explain to them calmly why the behaviour is not acceptable? then?..
Discipline
Step 1: 5 seconds to stop behaviour i.e5?4?.3?.2?.1.
Step 2: Naughty Step?child needs to sit on the bottom step of the kitchen stairs for 6 or 8 minutes depending on age. Use the egg timer and do not talk to them during this time. At then end ask for an apology and a hug. Please warn them of the naughty step before using it.
Step 3: Removal of computer time / tv time / pocket money / special trips depending on severity. Again warn them first.
NEVER humiliate, slap, smack, shake, bite or frighten.
Good Manners
We expect the boys to?
Always say Please and Thank you?.
Sit nicely at the table and use their knife and fork properly.
Please reinforce this?.
Rewards
WE praise constantly for good behaviour ?.
And always encourage their efforts?..
There are stickers in the dining room cupboard for all sorts of good behaviour. Please make us aware if there is very good behaviour.
Obviously, this might not suit you exactly, but you can adapt. You must go through this with your AP