I have finally (after many hours of persevering) gotten this to work! I am going to try to use evernote in my classroom to send assignments to students and have them submit work back to me with shared notebooks. I have set up a "mock" student in an account to see if it works. It works with this trial so I'm very excited about the possibilities. It may not work on a grand scale with a classroom set of ipads, but I'm going to try to do this. Setting everything up with computers first will take some effort but I'm going to give it a shot.
So, I usually don't make a habit of surfing the internet for posts about Evernote, but this set of posts popped up in my Google Alerts, so in this case we'll make an exception. Not here to spam either, just provide some constructive feedback (disclosure: I work for Evernote).
Anyway, I'm happy to hear you've got this working for you. We have teachers that use it in this fashion, and it's really exciting when it takes off that way in the classroom. Just to make sure things go smoothly for you, I'd first ensure that you're using the latest version on all of your iPads. If you're not, uninstall and reinstall the newest version. Second, ensure that you've sent the appropriate "share" invite to each of the Evernote accounts your students use, giving them modify status. Third, your account will need to be Premium, because only Premium accounts can give out modify rights to notebooks.You'll need to have extended modify rights to each of the accounts so they can access and make changes to your notebook.
Finally (and moderator, if you're out there, this may smell spammy to you, I don't know) if you snoop around on the website we have a bunch of videos and blog posts about how teachers and schools are using it. Could give you ideas.
Good luck!
(PS: I'd second the Khan Academy stuff. Their financial literacy lessons on iTunes U, in particular, are very very very good.)