Partner up the class. Break up one set of partners and assign one as a chaser and the other as a flee'er. The flee'er runs around the gym away from the chaser. If the flee'er is tagged, then he become the chaser. If the flee'er makes it to a pair sitting down, then he can sit on one side of the pair, bumping the person on the opposite end making that individual become the flee'er. This routine continues for however long you see fit.