Translation:The students study the Latin language in school.
Same mistake here. After talking to a native English speaker I think I got what was wrong. If you use the 'Latin language' you have to use the article THE. If you use just Latin, then you usually don't use the article. Examples:
I study THE Spanish language in order to improve my curriculum.
I study Spanish in order to improve my curriculum.
It's not the accusative nor the abative, but the DATIVE (but Duolingo never explains it). https://en.wiktionary.org/wiki/studeo studeō (present infinitive studēre, perfect active studuī); second conjugation 1. I dedicate myself (to), direct my efforts or attention (to), strive after (...) 3. (especially Late Latin, Medieval Latin) I study, I apply myself to learning. --Usage notes When used with a DATIVE studere means to have a taste or inclination for a person or thing, to keep close to it. Studere used with an accusative means to search earnestly for a thing, to desire and covet it.
I think you are wrong, but only where you wrote 'dative'. It's in fact ablative vs. accusative. For example: "pisces in pavimentum iacio"--- I throw the fish [pl.] onto the floor. "pisces in pavimento sunt" ---The fish are on the floor. Or, in Duolingo's own explanation, "in urbe" ---in the city; "in urbem"-----into the city (About the use of dative with STUDEO /STUDERE , that's a special case. With 'studeo' one must use the dative; it is almost as if it was an action you apply to yourself. "You give yourself to study". (Not a very good explanation, I'm afraid, but that's the general sense). A few other verbes have the same effect, for example APPROPINQUO /appropinquare, "to approach" (which occurs in Duolingo lesson 2 .5 "Gods"). With this specific action one must use dative as well. See https://en.wiktionary.org/wiki/appropinquo
"Prepositions in Latin must be used with one of two cases; the accusative or the ablative. Most prepositions “govern” only one case, a few such as “in” can take either, but with a change of meaning. “In” with the accusative means into, onto, against... it has the idea of forward motion, whereas “in” with the ablative denotes simply position, in or on. “Sub” can also take both cases. It’s also helpful to remember that expressions that in English require a prepositional phrase may be handled in Latin with no preposition. For example, the dative case is used to show indirect objects, or “to/for” expressions (...)"