i find someting to communicate with my groups of students, to view the list of there works and i can grade there works (ie gradebook), view list of there blogs (or profile), view the last news (ie the last publication or comments) of each blogs of the group.
the student can (download or upload someting)
i don't want to become friend with my students (like usual social apps) ie there no communication between groups of students
i use social apps or cms that i can add "manage group" module?
i think what you are looking for is moodle. http://moodle.org/ it has everything you are looking for. you could of course accomplish a similar thing with drupal and coding your own custom modules... but i think moodle is right for you, has it all built in.