Translation:She is a teacher at the elementary school.
Not exactly. In this case, no movement from one place to another is taking place. That means it is dative.
The English "where" can be answered with both dative and accusative. If you want to use a question word to determine whether you need to use dative or accusative, you must use the German question words: "wo" (dative) and "wohin" (accusative.) In English we have only one word: "where."
For example "Where are you going?" "I'm going to school" translate as "Wohin gehst du?" "Ich gehe in die Schule."
But "Where do you teach?" "I teach at the Goethe School" translate as "Wo arbeitest du?" " Ich arbeite an der Goethe-Schule."