Hi - sorry I've been out all day.
Ds1 has been having an hours tuition one evening a week since January and it has made the most enormous difference to him. After just one session he said he'd understood something he never had in class, the one to one was just what he needed and he really enjoys it. I never thought we'd be saying that about English!
Middle school were useless and wouldn't even test him even though infants had said they were pretty sure he was dyslexic, even after a doctors note, but he was tested fairly soon after he arrived at high school and they did some catch up work with him three mornings a week in year 7, which helped, but only up to a point, ie, when he was acheiving average results rather than below average.
He was in all bottom sets in year 8, which didn't help, as the learning environment left a lot to be desired [understatement!] and he had to work exceptionally hard all year to try and get moved up.We had really good support from his house tutor and with the extra English, which of course helped other lessons, he managed to make a huge change and he ended up winning the house award for outstanding effort and acheivement, which was FAB for his self esteem that had always been really low in terms of school.
We had to help A LOT at home, especially homework and planning, as he was so disorganised and had absolutely no idea how to go about projects for example, but by the end of the year he was pretty much working on his own and I just checked spelling.
He is now in middle sets for most things this year [top for PE] and really happy at school. 
We are carrying on with his tutor and in fact, she is also going to do half an hour first with dd who also struggles with writing and spelling, and actually she is nine and was fine with doing it after dinner. Though of course, they're all different, it's only been once, we'll see how it goes.
Maybe you will feel he's able to do it outside school when he gets a bit older, especially if it's his only issue with it. It is really hard trying to make the right decisions when they're struggling. He sounds like he's got lots of support though. Good luck!