not know which end is up
To be especially naïve, dimwitted, or uninformed. Give her a break—I didn't know which end was up when I was her age either. Local officials don't know which end is up when it comes to dealing with the housing crisis.
not know which end is up
Inf. not to be alert and knowledgeable. Don't try to hustle me, sister. You think I don't know which end is up? Poor Jed doesn't even know which end is up.