When you are in an interactive classroom, there are certain controls available to help you manage your experience, including making the content being presented by the tutor bigger.
This option can be accessed by hovering over the tutor's video and clicking on the three dots that appear in the top right corner.
This will reveal the option to expand the content to Fullscreen as shown in the video clip below.
Once you have expanded the tutor's video, you can return to the default setup by clicking the exit fullscreen view button that appears in the top right of your screen.