Manually importing users

Although its possible to script creating user accounts in the JSS via command line and the JSS API, I don't think there's going to be any way of getting the existing AD account password from AD and passed to the script.

Okay, I can pull that information from AD easily enough.

How can I upload say a CSV file with all the student data?

There's no csv file upload functionality, least not that I'm aware of. You may be able to use a csv file for input, but it would need to passed to a script that uses an API account with write privileges to create new users. I don't have such a script handy since I've never done it before, but if you give me some time, I can probably come up with something to do it.
One question though is, would those account passwords be in plain text in the csv file, or would you be putting those in manually later?

Lastly, is there any way you can connect your JSS to LDAP? I know you said you can't, but have you explored all options for that? Talked to JAMF about it? Because, really, that would be the best and easiest option here.

Our organisation pretty much said it can't be done unless we host JSS ourselves.

Perhaps I am confusing myself here. We are wanting to assign all our students (users?) to their iPad so we can easily troubleshoot issues.

The passwords can be stored in plain text, no issue.