My pupils always seem to struggle with explain answers. Perhaps some practice at this would be good for their mathematical reasoning as well as literacy. I use Eplanations : the four stages idea; 1. Can you explain it to yourself (in your head) 2. Can you explain it to a friend (tell them how you worked it out) 3. Can you write it in a letter to a pen friend (write it down just as you said it in stage 2) 4. Can you write an explanation for your Maths Teacher (the key words will help as your Maths teacher will expect you to use the correct mathematical vocabulary) Could they also write some instructions for things, maybe instructions on how to solve an equation or convert between FDP. Writing for purpose and audience is a good skill to practice. They could even write a page of a text/revision book for a younger age group and then pupils could try to follow their instructions or revision book to answer some questions on the topic to see if their writing makes sense.