Student work collected in a separate folder
Students work submitted through 'Assignment' option should be made available in a separate folder for 'Teacher only' access and student should not make any changes after submission.
Scott Letts commented
One solution that could solve this, as well as solving the 'students can continue editing after submission bug' is:
1) When an assignment is created, a corresponding folder is created in the Classroom files tab
2) Subfolders for each student are created with 'edit' access given to the student for their folder. The teacher has edit access to all folders. (i.e. Johnny can only edit/see his folder's contents, the teacher can see and markup Johnny's work as he works on it)
3) When a student submits their work the folder is set to 'read only' for the student and continues to be 'edit' for the teacher (Johnny can no longer edit his work and the teacher still has rights to edit/markup/comment on the student work).