In the Parler app on the class iPad, a teacher turns on class mode for their class. From then on the iPad shows only “Who's reading?”: kids tap their character, then their picture password (a few fruits), and land in their own books.
“I'm done”, or leaving the iPad alone, signs them out. A teacher leaves class mode by pressing and holding the lock and signing in.
Class iPads are set up in the iPhone and iPad app; they aren't available on the web.