Also, some student click done and start multiple times for fun. Then, other students do the same. You need to lock that down. Also, when writing on student's work, I would lie the option to not keep my feedback there. That way, the student can fix it himself or herself. I might show feedback in front of the class (with the student's permission) and not have this impact the student's work.

Thank you for the suggestion. We will be making improvements to this functionality in the future. For now, there is a workaround to prevent students from making changes. When you are done with a Handout activity, you can end it using the gear menu. Note that this will kick students out of the activity so they can't see and change their work, but you as a teacher can still continue to view student work using the dashboard.