I grew up with so many high-school romances my brain automatically assumes every single school romance I read is set in high school. Which makes it awkward if there's a lot of fanservice of them, like Yamada from Boku no Kokoro no Yabai Yatsu.
@guardian1102 "Shit-eating grin" is a reduced form of an rural USA colloquialism, specifically "Grinning like a possum eating shit" the North American possums tend to look a bit like they're smiling when they're messing around in your trash or whatnot, but it's similar to a particular human expression where you know you're probably getting in trouble for what you're doing, but you're happily doing it anyway. So it has the double-meaning that you're happily doing something that's going to make you 'eat shit' at least figuratively if not literally. It's seen on pranksters fleeing the scene of their deeds, or on people who anger someone just because they find their reactions funny. Although it's also seen on people who know they're doing wrong but are also aware they're immune to the consequences of their actions because they're rich or powerful or whatever.