Hi Marjorie, good to see you on here! And MadMathsMummy, hoping I can answer you too.
My DD2 is virtually the same age as your grandson, Marjorie - she'll be 11 in August so just clips into being secondary next year. We did look at schools briefly in case she wanted to go but decided against it - she's happy as she is and she is so little and emotionally young for her age that we all felt she would be ridiculously out of place in a secondary (I have pics on my profile, you'll see what I mean - neither DD2 nor DD1 age 14 are particularly grown up or streetwise).
Anyhow, because she's still very much a little girl in her outlook, we will just continue as we have been. She's been studying whatever has interested her, like rainforests or weather or animals, or lego or meccano or dancing, and I don't see why I have to stop that just because by a quirk of her birthdate, she will fall into the secondary category rather than the primary.
However, she's good at maths and science and we are already on secondary work for that as it was a natural progression, so we are really just going with the flow and tackling things as they come along, at a time and level that is right for her. I don't really see anything changing in September.
My elder daughter I took out of school at 12, and because I was in a panic about her not falling behind, we followed the Key stage 3 curriculum which is very accessible on the DFES website. I can link if anyone wants. However, after a year we ditched it as being a bit of a waste of her time and I won't bother with it for DD2. What I will do with DD2 is go straight on to GCSEs once she is ready and wants to. It's perfectly possible to take some early. DD1 is doing 3 this summer at only 14. The advantage of that is that she will never have the awful pressure of 10 GCSEs at a time that schooled kids have. We're planning on 2 - 3 a year for Year 9, 10 and 11, which will give her quite enough exams to do whatever else she wants to do with very little stress.
Far from putting pressure on her by taking some early, it's taken pressure off. We've worked only on the GCSE subjects and nothing else, so it's been fairly quick and painless to cover it and she's had loads of free time to do whatever else she wants to do. Because she's only 14, there's none of this "If I fail my whole life is ruined" feeling that children in Y11 at school have. If she fails, we'll try again in November and it won't matter at all.
Hope some of this is a help to you both!