you can make a desktop shortcut that will force the game into 720p, and even windowed if you need to
1. right click SussySchoolgrounds.exe, then click Create Desktop Shortcut
2. right click the shortcut, then click Properties
3. make sure you're in the Shortcut tab at the top
4. in the Target field add the following after the .exe" path:
-windowed -ResX=1280 -ResY=720
5. click Apply, and that shortcut should do what you want