This achievement is earned for finding optional photo #10. If missed on the first run, you can "Play Episodes" and select specific parts of the Episode in order to find the missing optional photos through collectibles mode
. The following collectible is described and can be seen below:
] - Optional Photo #10
Walk into Mr. Jefferson's class and take a picture of Alyssa in front of the window.
Collecting all 10 photos will also reward you with the following achievement: