Why not set up a new forum for "Student Assignments" so that students don't need to pretend it's a real life application anymore, we don't have to look at each new thread with suspicion and moderators would have somewhere to move such posts to when applicable.
If anyone wants to help them out then at least they know where to look.
I understand your thinking but if we continualy respond to student posts by just saying that it's an assignment then students will increasingly try and disguise their assignments as real world problems. Providing a valid forum for them to get help may avoid these issues. If students do continue to post elsewhere then their posts can be moved to this forum with no further comment. Obviously the quantity of posts will be seasonal but I think it may be worth trying.
Some less confident readers on the forums may be quite happy educating students while they're not confident enough to risk being flamed by users/moderators on other more active forums. This would give these users a comfortable environment in which to try helping others.
A dedicated student questions forum should explain in it's header that help may be given but not answers. It could also contain a few sticky threads that gave simple explanations for
how to recognise entities
how to get data into 3NF
Can the above points be shown to the other moderators?