Drupal 7 Display a list of reference node in node being display
You need to create a view of contents filter by Course content type. Now I assume you have a field name field_school. 

Add this field in Contextual Filter and select default argument Content ID from URL. 

When this block will be added on node page, it will automatically filters the courses of that school. Otherwise pass the school id as argument to view. :)

Here is the screenshot :