try some instant individual rewards. Explain / remind them of what you are expecting, especially for those transition times that you talk of. Then reward the first person you notice who has complied with this - I've used marshmallows for this with my Y3 class and they loved it. I make a big fuss, 'wow! you've done a brilliant job, sitting ready and listening and you deserve this...' Well you get the picture. I did this for a couple of weeks and it worked a treat, cost me about two bags of marshmallows per week. I just gradually eased off handing them out and they didn't comment at all, but continued to do as asked. Your class sounds very similar to mine so I know where you're coming from! I also used it to reward those chn who had made good effort, like the 15 or so that you mention, so when I saw great work, again I'd use the edible reward. It's not my own original idea, I stole it from another teacher. She used these rewards to good effect. She used a range of rewards from grapes, marshmallows, chocolate etc. I was impressed when I saw it in action in her lessons so that's why I thought it was worth a try. I guess you could call it bribery - but it worked.