How do you turn in apps on Google Classroom?

I am new to MIT App Inventor. How to you have students turn in a completed app in Google Classroom. I had the students screenshot their QR code, thinking I could scan the code with my tablet and grade it, but that does not work. Any advice? Thank you in advance!

Does Google Classroom let them upload files?
If so, well labelled .aia project export files would make good uploads.

Think of a Project naming convention that would help you organize them, like
Assignment01ABG.aia and have them do Project->Save As to rename their projects before exporting them and uploading their .aia files.

On that same note, can I upload/post an MIT App file in Google Classroom, and then have the kids download it so they can then upload it into their MIT App inventor projects?