Remember this is a learning process. Even experienced teachers have lessons they feel could have gone better. I think discussing your expections at the end of the carpet time would be a good idea - and then quiet reminders of classroom voices from time to time - praising those getting on with their work. Maybe asking individual tables to move instead of the whole class moving around (always a receipt for chaos). During plenary you can comment on those who managed to focus. As you get to know the class you'll also know whuch children shouldn't sit together! Mum xxxx