I will have a look at Interhigh, but I confess that I feel a bit daunted about trying to guide her through GCSEs, even with an online school as my support. And it would make it difficult for me to work at all, I would have thought. One year I might be able to flex (as mentioned I work contract), but to be out of the market for four seems risky.
I have wondered about the issues of putting her back into the same school (which then made me wonder whether in fact we should look for a different school). Truth is, though, I am very happy with the school as it stands, which is doing the best it can to help. Eg - the SEN has started something new he calls "forest school" - because he wants kids who don't enjoy school to have something that they can look back on that they did enjoy, and DD was one of the first to get the letters. She is enjoying forest school - where they take them out into nature and let them do want they want, even including climbing trees, and all the things DD likes doing, but it is one lunchtime a week, and not enough to compensate. He ended up putting DD on the special needs register, because she is too slow at everything, ie too slow to pack her pencils and too slow to unpack her pencils, and too slow to finish work in class (although she does it to a high standard), and takes too long over homework, and was just not finishing tests and exams (although doing them to a very high standard for the bits she got to - eg she would get 65 out of the first 70 marks of the paper, and then the rest up to 100 is blank because she doesn't get to it, regardless of what area is on the first part and what on the second. If given enough time to complete, she gets very high scores. So the SEN assessed her, and besides the fact that she took a really long time to complete the assessment, I couldn't make head or tail of what he thought he found, and I am not sure he could either, but something wasn't going right, so he said let's trial extra time in tests and exams, which has been fantastic, as it means she is actually able to show what it is that she really knows, but he cautioned us that when it came to GCSEs we may not be able to get it - because we need a diagnosis.
But this has been the pattern over the years. In Year 1 they were worried about the fact that she was still wetting herself periodically (whereas if she had deferred and been in reception, they would not have blinked an eyelid, as many kids were still doing that). In Year 2 that had cleared up, but they were worried that she couldn't hold a plastic cup without crushing it, or hold her pencil properly, and was not really playing with the other children, but playing by herself. If she had been in Year 1 I think that would have been regarded as within the bounds of normality. By Year 3 all that was resolved, except that because she was only then able to hold the pen properly, she had completely forgotten how she had been taught in years 1 and 2 to draw the letters, and her handwriting was dreadful. After jumping up and down at the SEN, I got them to give her some special classes focused on teaching her handwriting just as she would have been taught it in Years 1 and 2, and guess what, her handwriting came right. And all the way along we have had concerns because she cannot dress and undress herself for PE as fast as the others. But when she was taking swimming lessons with kids who were mostly the year below, there was never any complaint, because they were also by and large slower.
I really wonder whether it is not just that she keeps being pushed to keep up with an age group that is too advanced for her, and while academically she can mostly do that, whenever we have motor skills and the like involved, she just can't keep up.
My thoughts would be that the explanation she would need to give is "I took a year out to go visit my grandparents in Australia and my cousins in Brazil etc, but that meant I missed doing Year 9, so I have to do it this year". Kids don't know about LEAs insisting on in year admissions, or home schooling. But they can all see that if you don't do Year 9 of a three year GCSE, you could well be expected to do it again. Even if in fact we spent most of the year in Britain, the parts we didn't could be highlighted as the reason.