Lots and lots of in class repetition for multiple years.

And my memory is sketchy, but it may only have been select scenes. I’m looking at the page count now and I’m doubting that we performed all 210 pages.

Our last year of middle school we performed at least a portion of the play in a local German language competition that was mostly high school participants. In theory we only had to memorize our own lines, but most of the main character actors knew most of the other characters’ lines, too, for whatever portion we performed.

EDIT: I expect most (native speaker) adult performers of it have nearly the whole thing memorized, though. Props to them.