Thanks so much for your replies.
Well the worm has turned again. His teacher really was having a bad day and, as she's so busy, I suspect she didn't appreciate the unannounced visit.
I dropped in to my son's classroom yesterday morning and we organised his tote box with clear plastic folders etc so he can find things more easily. His teacher was excited by this and pulled me aside.
She said she might have given me the wrong impression the day before because I seemed to have a shocked look on my face.
She said she didn't mean he would have to repeat year 4 but should stay in the 4/5 class as a year 5. She apologised. (I'll have to get my hearing checked). I thanked her and she noted she thought my idea of asking the learning support teacher for ideas on strategies for getting him to be more organised was a good one and that 'whatever we need to do we'll do; we work together!!!'
Anyhow, I used the opportunity to remind her of his fear of failure stopping him from proceeding through exersizes and tasks if he perceives he can't do something. She acknowledged she had been leaving him alone to complete things as she hadn't wanted to pressure him.
Yesterday when I picked him up he had received an in-class award for being organised all day and had managed to complete all his tasks for the day (with his teacher gently encouraging to keep moving forward in one task he seemed to be stuck on). Woo Hoo!!!
What a roller-coaster!!
Thanks for the support and advice Grinity and cym....very much appreciated.