Paired loops is also good. You divide the group into 2 halves, those who are confident and those who aren't, or fast and slow..........depends on your choice! You pair them up one from each group. You need a track or a short circular loop. The fast runner starts off running fast in clockwise round the loop, their partner the slow runner starts off in an anticlockwise direction at an easy jog. When they meet they swap speeds but turn round and run back the way they have come. So now the slow runner is running fast in a clockwise dierction and the fast runner is recovering at a jog in an anticlockwise dierction. Repeat 3-10 times.
This works well for a mixed ability group, and noone knows exactly how far or at what speed you're all runnning, so a good intro to faster running too.