May I suggest some basic positive classroom management techniques plus some other stuff I've found useful along the way?
Mean what you say. Do not issue vague or impossible to carry out threats. Carry through. eg, If the television is the problem and interfering with the morning routine, switch off the television and ban it for following day. They have to do the crucial things (like getting dressed) before they do the fun things.
Don't raise your voice, drop it the crosser you get, both in volume and pitch. You won't get a sore throat and they will respect you more for keeping your calm.
Try giving a sweet to the first child to do what you say. Not the second, or the third, only the first Very surprisingly effective even in a class of 30 unruly 15 year olds.
With my children I introduced a "points" system which was surprisingly effective. You may to defer this until the children are listening to you again (and they will, have no fear). Basically every child starts with 10 "points" in the morning. 1, 2 or 3 points are added and deducted to the total whenever the children do something praiseworthy or reprehensible (depending on your view of what is praiseworthy or reprehensible). So for example, helping your sister find her shoes--> 1 point added, pulling your sister's hair, deduct 2 points, etc etc. At the end of the day, those with 10 points or more had a flake on their ice-cream. The others just had ice-cream. The point of this was not to divide the children too much- if one/some had had ice-cream with a flake and others nothing, resentment would have built up and they would have rebelled.
"Good deed bad deed" jars. My friend did this but I'm not sure how effective it was. Involves beads/pebbles etc in two separate jars and treats when the good deeds outnumber the bad.
At all costs avoid tarring them all with the same brush! Do not issue "class punishments". Avoid also issuing public dressings down. Speak quietly and confidentially to the problematic child and make sure they know you mean it.
Do not overlook the same behaviour in one child that you pick up on in another. Age is no excuse- they are all working towards the same goal regardless of age.
Get out of the house and to the park/walk every single day without fail, even in poor weather! Exercise the little sods cherubs into tiredness.
GOOD LUCK! It's really hard but you will manage. Underneath this inchoate poor behaviour are some loving and well-behaved children. They just need to find their way out.