When it's worth it you won't hear anyone complain about "the grind". In this case, it's not worth it.
My perspective on "grind" might be a bit skewed after spending way to many hours over the last two decades playing MMO's. But TBH, I didn't even notice it really.
What is the reason behind a spec op being yet another powerless, gullible JK girl, other than to fulfil 'barely legal' fantasies?
Actually, some of this was answered in game. I'm pretty sleep deprived atm and spacing out a bit, but please bare with me.
Basically, they want negotiators and spies(not like movie spies) and not spec ops, and ideally they seem non-threatening. Personally, I feel like pointing out that even IRL negotiators will get hand to hand training, just in case, but whatever. Also, lore wise it's not a highschool. Basically, there was a plague that wiped out a huge chunk of the population. The school they send you to is meant to help people adapt to the modern society- which is kind of a light post apocalypse setting. This includes helping people retrain if they were colledge students going for a degree that aren't practical.
In practice, it's a bit too much like highchool to really work as the lore is written, IMO.
Sammy get's shoved into it mostly because she has some memory problems, plus being in a coma during the entire plague thing. Which is also why her mind stat is shit from the get-go.
Technically, there is no punishments for not going to school, and you can ignore it. But it can net you 1-3 on every stat (except confidence and by extension, mood.) during a day independent of anything else. Plus, dancing is profitable, and if you make friends with the soccer team, you can eventually get into stupid bets with them and that can also be rather profitable.
Sammy's participation as a fixer isn't actually mandatory. They were actually willing to more or less let her walk with their experimental body- although I imagine they'd be monitoring her for data.