To dream you are looking for something in your locker means you are missing or seeking something in your life. If you can't find what you're looking for, it means you may get into trouble in real life if you haven't already, or that you're not living up to your responsibilities.

To dream you are cleaning out or organizing your locker means your life could use some cleaning out and re-prioritizing.

To dream that you can't open the lock on your locker, or you can't remember the combination, means you are under stress and afraid things won't go well, or could mean that you are sabotaging yourself or holding yourself back from success.

In particular, to dream of a school locker, denotes hidden feelings, knowledge, and attitudes that you need to learn and/or acknowledge.