Your description of what you are doing to get your students on-task sounds very good. You deserve credit for being willing to share this.
I think it helps to have a totally quite beginning ritual skill building assignment that they get from a poster or the white board, a note on their table, or in some other way that automatically gets students immediately on-task with absolutely no chance to horse around.
This way the teacher might have a chance to spend some quiet one-on-one time getting to know individual students while they work. When a student does not follow the prescribed routine as they come into the class, you may have to ask, "What do you not understand about starting your work?"
I know one teacher who formerly ran a business. He is a manager. His class is greeted with a printed agenda for the whole period on every table every day. His students work and they learn. I never felt like teaching this way because I wanted students to learn to take more responsibility for their own task planning, but we all have to figure out a style that works for us.