Sorry for this non-visual guide, but getting this hat is pretty simple. Go to the school, located on the west of Omnet town (titled on map). Upon entry, you will notice there are lockers which can be open and closed upon grabbing them. Above each of the top doors there is also a moving clock, which is key. When the clock hits 12:00, mash the grab button and hopefully you'll get a popup saying look what you found in the locker. Be quick though because the hat won't spawn unless it is from 12:00-1:00 (not real-life-time).

Feel free to post any corrections.  

Become a dunce.
Have you tried skipping school or throwing paper airplanes during class?  

Too bad being in the corner isn't a thing in graal school.  

Thanks. I will provide you with pictures if you wish.