Cinderella, don't worry, I'm sure it's something that will come.
I don't know how old your son is, but getting him to focus on the five senses is another easy way to create atmosphere and enrich his writing. Pupils often tend to limit their description to what they can see, ignoring touch, smell etc
I don't think the use of imagery has to come naturally, he could just have the awareness that it would be good to include eg a simile and a metaphor in each story...
Sorry, we double posted Cinderella. I think it's knowing the word and also when would be an appropriate context to use it so if you have a sick old man how would he speak, a witch, a schoolboy who has been running etc.
You could also use postcards and cut out pictures from magazines as a good way to stimulate creative writing.
I think it's teaching your DS to have the awareness of language and its precision rather than stock phrases. It's just imho
Right, back to the unpacking! My hubby will be back at the weekend and I'll still be surrounded by cardboard boxes.