This is just a "theoretical" query for the time being...not knowing much theory, I couldn't figure out from the online theory syllabus whether fugue is covered in any of the grades.

Can anybody tell me which, if any grade, covers fugue?

Also, recommended listening or study resources for studying fugue? Son has a way to go before starting fugue, but theory teacher warned him that one university here has a separate entrance exam just on fugue (if you pass the harmony exam first, that is). And a general fugue thread seemed like a good idea anyway!

Very recently, on the forums, there was another discussion on fugues. The wikipedia article on fugues is a good starting point for studying the theory.