My sons had this same trouble at 10 years old. If you have a way for him to record his oral narrations, it might help him in the first several months of writing his narrations. If handwriting is an issue, have him begin a typing course and use the keyboard to write his narrations.
I used IEW methods with all of our older children. Our youngest son, 13, has background in IEW, too. It was a step-by-step process that I turned to years ago as I hadn’t found CM suggestions for formal writing at the time. I combine CM methods and IEW for him, based on what I’ve learned over several years of trial and error. It seems to be a long, drawn out process for many boys.
With our boys, I’ve seen a natural progression in abilities over several years’ time. I’d say, the fear subsides around age 12 if you begin as early as 10. Just getting one sentence down in the beginning is a struggle. If you have him record his narration and write a sentence per day in the beginning, or use a timer for 5, then 10, then 20 minutes, he will build stamina over a year, or so.
I highly recommend reading Lindafay’s series on the transition from narration to formal composition. It’s very good and will save you $ and reduce your stress level. Seeing it as a long term process lightens the load.
http://www.charlottemasonhelp.com/2009/07/narration.html
HTH,
Becca<><