Google has just released an iOS and an Android Classroom app, and it gives option to take pictures of your assignments to submit. When installed on a phone, it comes up along with the list of apps you can share with from within another program. You can, for instance, upload drawings or PDFs from within an art app or Google Drive. It also caches its contents upon launch, so teaches can access a student's work even offline.
Other than the new mobile app, Classroom for desktop now shows teachers a list of assignments, giving them a clear view of what they've already reviewed and what they've yet to look at. Even the most competent educator can get overwhelmed by years of student-submitted work, though, so teachers can now archive past classes in the program if they want