Assessing children's written responses to stories, poetry and song

If you were to assess children written responses to stories, poetry and song. How would you assess it? For example, children have to be told to write their own friendship poem, review a book and also to review a song. How should I assess the childrens written work?

Well, what do they know about those things? That is, what have they been taught? After all, first we teach, then we assess their ability to do what we taught them, right? :-D