Kind of school mark covering reading and writing, perhaps (7)
I believe the answer is:
grammar
'kind of school' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
(Other definitions for grammar that I've seen before include "Study of word and sentences" , "A language's syntax and morphology" , "Study of basic linguistic units" , "Branch of linguistics that deals with syntax" , "Syntax etc" .)