I would translate that one as "Nincs semmi jó az iskolában."
They mean kind of the same thing, just two different ways of saying it.
It's not particularly important. It could as well be a general statement about schools.
Sounds like a school I taught at years ago in Florida - a broken down building in an inner city neighborhood. No working bathrooms on the first floor, no science lab, etc. 1969-1971, 15 years after integrated schools were the law of the land. The state claimed the schools were "separate but equal." NOT! Sorry! Had to say!
I don't think this is what was intended by the Hungarian sentence. I think they meant something like a student complaining that "there is nothing good about school," but of course not as a literal translation. If that is what DUO wants they are barking up the wrong tree( LOL) because you have to consider idioms when you translate from one language to another!
You have to see what the is (or sem in this case) in the Hungarian refers to. Here it's saying "semmi sem", so it refers to semmi. That makes it mean something like "nothing as well", which doesn't really add anything to the sentence and doesn't warrant the use of "either" in English. In Hungarian you can say "semmi nem" just as well with the same meaning.
Now if were something like "Semmi az iskolában sem jó", you would translate it as "There is nothing in the school either that is good", because you're adding the school to other places where nothing is good.
"in the school" means in the school building, "at school" means level of teaching, education etc. Either both should be accepted, or the Hungarian sentence should be more precise.