A mistake I think teachers often make is that they don't think about what writers need to do when they write. We don't just sit down and whip out the first draft that is a perfect draft. We mull a writing problem over for several days. We scratch out some notes and outline our ideas in some way. So it's a mistake to throw a long writing assignment at the class and a due date and then do nothing in between.
Writing has to be approached in stages.
The content of a term paper is often weak because it represents a first draft. It wasn't taken through the process whereby students discover the meat of what they want to say and the evidence for it. Teachers can make sure students don't do papers too quickly by putting things into steps. Write out the assignment explaining not only what to do but how to do it, what recommended procedures to follow. Whenever possible, allow students to choose topics that matter to them.