Did you try this?
The additional blocks on dashboard like private files, online users, latest badges, calendar and upcoming events are now visible only to admin and teachers and are hidden from students.
The setting for this is done as follows
Go to Site Admin -> Appearance -> Default Dashboard page;
Turn blocks editing on
Click on the settings icon for 'Private files' block
Click on 'Permissions'
In the row 'View block', under col 'Prohibited', add 'Students', 'Authenticated user on front page', 'Authenticated user' and then click on 'Back to block: Private files' at the bottom
Repeat steps 3-5 for the other blocks, i.e, calendar, latest badges etc.
After this, click on 'Reset dashboard for all users option' (available besides the 'Blocks editing' option)