Sometimes I have classes so close to each other and I am moving from one place to the other it becomes hard to pray on time. Is it permissible to pray in the train or bus? Is it permissible to pray in a locker room as I have nowhere else to pray when i arrive to swimming class.

by

You can pray in the locker room, if it is permissible, otherwise, you can delay your prayer till you reach home, if you will reach home before midnight.
However, if you were neither able to pray in the locker room, nor able to reach home before midnight, then, you need to cancel your swimming class.