This is along the same lines as the Let us schedule a Publish Date / Time for Content Pages request. It would be ideal if assignments could be set to publish at a given time. Currently there is no option to completely surprise the students. Even if the assignment is locked (or the module the assignment is in is locked) they can still
- See that an assignment exists
- See when it will be available and
- See what it's called.
The current option is to have someone manually publish at a particular time.