A little bit of organization goes a long way. 15 minutes of getting organized is probably as productive as 2 hours of substantive work. As long as it doesn't take so much of your time that it crowds out the substantive work.
It clears and focuses the mind, makes things seem simpler by removing artificial impediments.
It is actually substantive, in the sense that these are tasks that need to be completed.
It is not inherently time consuming. For example, take the task of figuring out which dates your class meets. You can sit down with a calendar and figure this out in a few minutes. At the same time, it frees up time later by increasing efficiencies.
It doesn't necessarily require great intensity of concentration.