"They had tested the students before the breakfast."
Translation:Sie hatten die Schüler vor dem Frühstück geprüft.
Yeah, I put the same and lost a heart. I thought for a moment that was because of the rule Akk. before Dat., but I checked and that happens just if both objects are nouns! (http://forum.wordreference.com/showthread.php?t=698884&langid=24). Someone please explain!
The verb object normally comes after the verb and before the adverbial modifiers (which form part of the mid-field, or *mittelfeld, that comes between the verb object(s) and the verb complement at the end of the sentence).
"geprüft" is a participle. It doesn't change according to person or number. The only verb that's conjugated is the auxiliary "haben".
Give these a thorough read:
Can we say "Vor dem Frühstück hatten sie die Schüler geprüft" too? I think it is like saying Morgen dürfen wir zu Hause gehen versus We dürfen morgen zu Hause gehen. In the first sentence, is put in evidence the point of time, in the second is put in evidence the action. "Vor dem Frühstück hatten sie die Schüler geprüft" is a little different like saying "Sie hatten die Schüler vor dem Frühstück geprüft". Dear experts of German, am I right??
Not true. Vor/bevor are used differently. Bevor is a subordinating conjunction, whereas vor is not. Vor is used in prepositional phrases. Bevor ich zum Markt gehe, muss ich meine Mutter schlagen <-- Requires bevor here (vor is wrong in this context). Vor der Prüfung, schlage meine Mutter (this context requires vor, whereas using bevor here would be wrong).
"bevor" can't be used in a propositional phrase, it is used in a subordinating clause and thus is accompanied by a verb instead of a noun. So it wouldn't work here since we just have "before the breakfast". You would need something like Bevor die Studenten gefrühstückt haben, hatten sie sie geprüft. (Before the students had breakfast, they had tested them.) However, this would not match the sentence from the exercise.