The following is for teachers who already have their classes in Google Classroom.
You can select the students and then give them the sharing right to a folder/document/spreadsheet/slide easily with the email generated in Google Classroom.
You can also select the students which you want to give the rights to for a particular folder/doc/slide/spreadsheet rather than select all.
To select the emails - click on the first email then press shift and click on the last email to highlight the email. Press Ctrl with C to copy
