If you want to be discrete and avoid distracting your users with ads of  your school's course , check how easy it is to remove it by just adding a code snippet.

1 Copy the following code snippet:

@media screen and (min-width: 650px) {
  #inboxWrapper #firstCol {
      width: 30%;
  #inboxWrapper #secondCol {
      width: 70%;


2 Navigate to Appearance->Built-in pages CSS and paste the snippet in the Text Editor window.

3 Save and the banner will disappear once and for all! :)