I think about the only subject where they assume that children have already covered certain topics is maths, so it might be worth having a look at what the NC would cover on that by the end of primary, and check that he has a reasonable understanding of most of that.
Otherwise, so long as he has plenty of chances to read for different reasons, to investigate things, do something creative, something good for gross motor skills and something good for fine motor skills, then he will be developing his skills in a good range of areas.
If Ancient Rome and UFOs are his interests, then he can get skills by looking at those. But you might want to push him to develop some "critical thinking skills" on the UFOs, so that he can learn to weigh up whether books, websites etc are decent science or just "out there" ideas!
I'm coming to the conclusion that many schools just want "average" children who don't have "pushy parents" [encouraging?] and I think the curriculum is restrictive to children who have a love of learning. I believe, certainly at my DS's private school, that they spend a lot of time helping slower children to catch up but neglect those who are more able and behave nicely: they will always achieve well in the tests and exams so nobody has to put in much effort. Many teachers, however experienced, dedicated and knowledgeable they are [and I do believe there are many around], are forced to do a lot of recording and box ticking, leaving little scope for "branching out" and veering off the syllabus.
The NC isn't everything and I'm sure you would tailor your DS's education to really mean something.
By an acceptable level I suppose I mean that I don't want him to fall behind and suffer later on if he does go back to school. When I informed the school I was removing him to home educate the HT said that I was "screwing up his chance to have an education".
His current interests are Ancient Rome and UFO related things. He reads anything he can on these subjects and really goes in depth so I can see that it's not something most children his age would be into but he loves it so I don't want to discourage him.
Don't have time to post much now but I think your biggest thing will be changing your idea of what "normal" looks like.
How to keep up social interaction Your son does sound ASD, to me (my DD is but was HE until 18). You may find specific interest groups (chess, sports, music, drama, wargaming, etc.) more useful than general groups - he'll then have people also interested in that topic and won't have to make small talk. (Read the thread How do you sucessfully HE an Aspie? Despairing here....)
How do I ensure he progresses at an acceptable level? If I decide to send him to high school in a few years will he suffer from not having followed the National Curriculum? He won't suffer from not following the NC - particularly not if he is intelligent and mature. What do you mean by "an acceptable level"? If he is interested in stuff that they don't do in school (a foreign language, quantum physics, arcane maths, programming) then he'll have time to concentrate on those things. Unless you are concerned about his maths and English, you do not have to bother about them too much - daily life will allow you to do many activities and if he wants to pass an exam in them later, you can deal with the necessary skills when he has a purpose for them.
Due to a combination of circumstances I will be home educating my 9 year old from next week.
I have read through a few threads here, thanks to those who have taken time to collate lots of information, it is very helpful.
My main concerns are:
How to keep up social interaction, my son doesn't really have any friends from his class that we could keep up with. Really he's seen as 'odd' by his peers and he does struggle socially. Over the past few years three staff have questioned whether he has asd. I did get a referral to a paediatrician but he dismissed concerns and discharged him after the initial consultation, he said A was intelligent and too mature for his age so would stand out from his peers.
How do I ensure he progresses at an acceptable level? If I decide to send him to high school in a few years will he suffer from not having followed the National Curriculum?
A was becoming more and more unhappy and anxious going to school, bed wetting and it came to a point where I felt it was better to remove him. The school weren't very supportive, they kept telling me they didn't notice any problems and that he was happy in school. I felt like they thought I was inventing problems. His teacher did admit he didn't 'fit in' but said he needed to learn to like the things his peers are interested in and that he talked too much about things no one else was interested in.
Thank you if you have taken time to read this, any advice is most welcome. Hopefully I have covered everything, any questions please ask.