This morning we released, by your request
Subject creation - just type a new subject name into the add course dialog and it will show up.
Course deletion - instead of just hiding the course, you can delete it - it deletes any lessons you have for that course/student in the current period, so be careful!
Note that if there are other students using that course, or other lessons, it can't really be deleted. Delete it from all students and the course will be deleted.