Duolingo translates "Where is the classroom for the Japanese class?" as 「日本語の授業【じゅぎょう】はどこの教室【きょうしつ】ですか？」.
I don't understand the construction 「…はどこの教室…」. My instinct would have been 「日本語の授業の教室はどこですか？」. Are both used? In what circumstances?
My first idea was that this is a の-adjective, with a literal translation of "The Japanese class has a where-ish classroom" but the 「…か？」 at the end tells me that is unlikely.
Both your instinct and the Duolingo sentences are correct. The sentences can be translated a little differently, but there's no fundamental difference in meaning.
日本語の授業の教室はどこですか？
Where is the Japanese lesson classroom?日本語の授業はどこの教室ですか？
Which classroom is for Japanese lessons?
I translated どこの教室 as 'which classroom' because that is natural English. Obviously its literal meaning is "Where's classroom", but here I think the Japanese choice of question word is more logical than the English.
I'm starting to speculate now because I'm not a native speaker, but I think that having long lists of nouns joined by の is considered bad style. I think two のs is fine but more than that starts to look clunky. So even though your sentence only has two のs maybe the Duolingo one would be slightly preferrable.
