Privacy or ownership.
Having authority over one small area within a larger area (such as being responsible for one aspect of a group project).
Looking for something in your locker can represent a desire for something (answers, information, etc.) or searching for something you’re missing or you’ve lost (your identity, motivation, etc.).
Cleaning out or organizing your locker could represent cleaning out or re-prioritizing some aspect of your life (or a desire to do so).
Not being able to unlock your locker can represent feeling stressed, afraid things won’t go well, wanting to do well, or holding yourself back somehow.
See also: Cabinet, Storage, Lock, Security, Privacy, Unlocking [1]
Dreaming of a school locker also denotes hidden feelings that you should recognize in yourself, or knowledge you should learn. Also see “Locker Combination”, below. [2]
2. Long hidden or repressed emotions or problems (to see a school locker).
3. A phase of uncertainty, confusion (to be unable to open a locker). [3]