You don't have enough sample data to make a line chart. If you set your sheet up like the following, you would get a line chart if you had more than one date per student/subject. You could clean this up a lot, turn of grid lines, rename axes, etc.
Here is a sample from Superstore with more data
Book1.twbx 1.2 MB
Just we have to break down the report by adding the addition & meaning ful dimensions to the view.
For An Example,
We are showing Region wise Sales on the view. Once you add the secobd dimension Tableau Automatically split each region into different categories based up on the second Dimension value.