Try countdowns, 5 -->1 and 3 --> 1 (vary this with tone required), use a mini-bell for getting them back/attention. The other thing I was doing with year 2 which worked a treat is writing the names of pupils that don't listen or misbehave on the board. Make it clear that these pupils will miss their playtime or other activity if it continues. Also get them to stand in the corner of the room in silence without leaning on anything. Yes the younger ones can be naughty but with ground rules in place EARLY then it is easier. The only problem is that following up unruly children's parents may be tricky in a 'supply' capacity. If you can have a stimulus of some sort to constantly get them engaged i.e. use of interactive whiteboard, a pet (this is extreme), but make it fun and show them your softer human side too.