The best way to improve your ability to think is to spend time thinking.
Writing comes at the end of the sequence of Listening, Thinking, Speaking, Loud Reading, Reading to oneself and then Writing to communicate our thoughts & then writing to clarify our thinking.
Role of writing in learning math changes as children move up the grades.
1. Learning penmanship - Preschool & Lower primary
2. Expressing math ideas, operations & procedures in writing using appropriate vocabulary- Upper Primary & middle school
At stages 1 & 2 too much writing in the class will interfere with learning. At the same time, neuroscience research shows that the process of writing strengthens our cognitive neuro-connections, which is important at these grade levels.
Hence the writing work can be given as homework.
3. Using writing & revising as a way to sharpen our thinking - middle & high school
It is at this stage that good writing requires good thinking. One way to force yourself to slow down and think is to write.
Clear writing gives poor thinking nowhere to hide, making a lack of understanding visible.