We have a similar story, DS was finally diagnosed with auditory and visual processing difficulties just before his yr6 SATs.
He could read, understood the text etc but hated it- would do all he could to avoid it. However, he would listen to stories and loved audiobooks. His idea of Hell was reading aloud, much happier reading in his head.
Spelling was (still is) abysmal and his handwriting, while legible, is terrible. Lack of ability to follow simple instructions lead to daily rows and meltdowns (shamefully often on my part).
However, he is bright- currently in top sets across the board, albeit in the middle of them rather than at the top- so he coped. He was brilliant at managing to hide what he couldn’t do. He can’t copy the date from a board, but the person sitting beside him can- so he’d copy it from their book. As he was achieving and would pass his SATs (he did, even the spelling and grammar as he can do the grammar) there was no money for assessments. I’m also s teacher- I know that there really is no money in schools, I understand this.
He was assessed and treated privately by a behavioural ophthalmologist. It was the best money I’ve spent, if only to teach me how to work with him better. I was doing it wrong for his brain. The assessments were about £200. Follow up appointments are a bit cheaper. He was review at the start of the year, new tinted glasses, new shade needed as his needs had changed a bit, £360 including 2pairs of glasses. I winced, but I’d been aware this would need to happen so prepared for it!
Like someone upthread said, I cried when he was diagnosed. Not because I’m sad or disappointed. It was sheer relief that someone understood my boy- what life was like. To understand what he genuinely finds hard is a massive relief. There are no excuses, I gave him back some homework last week and told him it was rubbish and he needed to re-do it (he’s in yr9 so old enough to be told these things honestly!). I will back him up completely when he needs support.