When you de-cross list NO STUDENT DATA will move over to the other courses. In essence it will be lost; all grades, submissions, discussion posts, etc from all students in the sections being de-cross listed. In reality the data is still in the course but once you remove the students from the course you can't access it anymore. To me this seems a bit scary to do on a course that has already been used for a significant amount of time.
If you are going to move ahead you could use commons to replicate the content into the previously unused courses, or simply go into each of those courses and Import the course content. Given you are talking about 6, using Commons might be more efficient since you can select all 6 at once to import the content.
Rick
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