I've done both.  When we first started it took way to much to have them sign up and sign in with their own.  I recommend (if you haven't already done so) asking your tech department to get the app installed in the Google waffle as well. My students love that they can sign in to classroom/drive and scroll all the way through to find the icon.  

Thanks and take care,

Valerie Grabek, MSLIS

Teacher-Librarian

Windham Middle School