Homework, perhaps, heads of school always read aloud (5)
I believe the answer is:
essay
I believe this clue is a double definition.
'homework perhaps' is the first definition.
'heads of school always read aloud' is the second definition.
(s, a, head letters of school, always, read aloud)
(Other definitions for essay that I've seen before include "Short literary piece: attempt" , "Trial, piece of writing" , "Composition; attempt" , "School compeosition" , "Try - composition" .)