1st one goes to the other side, 2nd one follows after x number of steps,...
Start simply by having the first student walk to the other side around a cone (indicate the rhythm), followed by the second student at x number of steps.
Do the same, students are lined up in e.g. 5 rows, each time walking in pairs.
Only then switch to per 3, per 4, etc. Finally the whole group in a row.