Part of the problem is that kids (especially bright kids) expect the assignment to make sense. They're completely stymied when they can't see the point. In this case, there isn't really a point -- the teacher just wants the kids to write something for the sake of writing something.
Well put. I really do not understand the point of open ended writing assignments for early grade students, for the most part. I can tell you, this process has just about sucked the life out of writing for my ds. There are SO many more creative ways to ask kids to write if they are stuck then to wait out a kid staring at a paper for 20 minutes.
You're right about assignments making sense. My ds would ask me WHY his teacher needed to know what was going on in his life every day (lol) by asking him to write in a journal. There wasn't any logic to it.
Just as an aside, I think this is why math works better for my kiddo--it's sequential, has rules to follow, and it's own "language". It makes sense.