I have space to line students up that helps and we have a clear consequence system. 4 consequences and they are removed and have a lunch time detention, an after school detention and a letter home. Where you place yourself in the room matters and an way of recording warnings - I use the seating plan on idoceo. You don't want to be turning round to write names on a board when a class are playing up.
i also have everything out at the start of a lesson. At the end of a lesson a class give out books for the next class. If they need to get equipment during the lesson there is a clear time to do that, I usually say 2 mins for the class to collect colours and then the chance is gone.
This is my routine with every key stage 3 class
Line up outside the door. When they are 95 % settled and looking my way I tell them they will enter the room in silence.
I then stand at my door boundary and they are silent as they enter my room. They will stand behind their chairs in silence when they enter. I don't leave that position. If they speak they go to the back of the line and get a warning.
When they are all in the room I stand at the front and say " I am scanning the room now to check for silence". Anybody speaking gets a warning. I deliberately let the silence hang to show control.
They then sit down and have a task to do in silence whilst I do the register. Again if they talk they get a warning.
Nobody talks when I do or when a student is contributing or that is a warning.
During the lesson they will also do some silent written work. I set the task, check for questions and they say " we will now work in silence for .... minutes, I am now going to stand here and watch"
That works. The word silence is key. Be quiet is open to interpretation.
If they get 2 warnings in a lesson they get a note on their SIMS behaviour record. If they get 3 warnings they get a note on their SIMS record and a detention.
As a head of faculty I run behaviour reports every week. Any student with 2 behaviour points on the system within a half term from the same subject gets a letter home. If they get to 4 ( hasn't happened yet this year) we will remove them from lessons and in invite parents in.
We also do lots of positives. Student of the lesson, lots of merits and lots of contact home for good reasons.