Why is it going back? I think "going back" and "comming back" are two different things!? Going back sounds to me, that the pupils are on the first half of the track. (They started a few seconds/minutes ago) And comming back is on the second half near the school! (So, they will arive soon).
The meaning of both expressions is the same. What is different is the point
of view. From the point of view of the parents "Students are going back TO school and coming back FROM school".
From the school point of view "Students are coming back TO school and
going back home".