Man, I feel like this could be so good, but this comments section alone points out way too many flaw:
     Why do they not care if everyone has to pass for them to pass the year? This girl is clearly not studying? Author forgets all his plot constraints.
     Characters suck. They all say nothing. We know nothing. They have no aspirations. They suck. We aren't learning anything about them in these pointless classroom arguments. They suck.
     No adults. Ever. No explanation as to why not -- except for this girl, but it's meant purely to get more sympathy from the readers.
  
That said, I still see the potential:
    The characters seem interesting if we actually learned anything about them. The air of mystery is working at least.
    I'm starting to like the MC because he's starting to do thing. Even if it's incidental and/or awkward.
   The MC White-knighting/being a good person. It's a fine line between the two, but if he's just a good person, making the MC likeable by fixing some of his other flaws will be great.