"When did you find out your notes?"
That's surely not a valid translation.
In this context, "Noten" only translates to "grades" (US) or "marks" (UK).
In America we would often say, "When did you get your grades?" Of course "find out" works too but "get" seemed the most natural to me.
Where is "did" in the context?
The combination "habt erfahren" would literally translate to "have found out." But in English we would not say, "when have you found out?' we would say, "when did you find out," so "did" is a better translation for this sentence.
"Wann habt ihr eüre Noten erfahren?" is given as the correct sentence when it's presented as an audio question: that umlaut has to be an error, right? (Reported, for what it's worth...)
I put when did you find your grades out which is what we'd say half the time. Reported but correct me if im wrong.
Yeah, sounds good to me.
I put "When did you receive your marks" and was marked wrong. I am reporting it.