Ideas for games to get kids running round track kids?

Ideas for games to get kids running round track kids aged 7-11 and in group sizes of about 25 - 30.

It depends on how far you want them to run. For the likes of a 50m run, I have found that if you split them into 2 groups of 8 and have 1 group at the start of the 100 and one halfway to the finish, give the group at the 50 bibs or something similar and use them as tails. The group at the start has to get a tail before the group at 50 reach the finish. Things liek that work pretty weel

Our kids really enjoy a continuous relay, where we have teams of 9, spaced every 50m around the track. They continue the relay until they get back to their stsrt point. With 9 kids in each team, this will give a total of 9 laps. Numbers in each team can be varied - less kids give longer legs, more kids and they shorter legs.