This is happening due to a combination of a long course title and the padding that is created when the font size is set to 10.

Basically, when you set the font size to 10 it bumps out to the very limit where it creates space for a course with a long title. It doesn't actually wrap the 
course title but creates the space if it needs it. This is something that font size 10 does in this Report Card. To fix this, make at least 1 Course that each Student's is enrolled in Course Title 24 Characters long (it could possibly be pixels as each letter is a different width W is wider than I) so larger letters will take up more space which adds the double spacing. If you do not want double spacing, then it would be best to shorten the longest Course Title so the double spacing does not happen.