Membership system considering potential future expansion

I want to add a membership system to my classroom website, so users have to log in and have a unique ID as well as their real name, so I can only allow actual students to view the materials.

Is there a good way (whether it’s plugin or something else) to do this, while bearing in mind we might have a custom app in the future – so we’d want to be sure we could use this same membership system outwith WordPress.

I’ve never done anything quite like this before and while I’ll be working on the WordPress, I won’t be working on the app – but I don’t want to setup a membership system that isn’t compatible with the app or any other external uses in the future!

Thanks for any advice