I did a search on MN and found a lot of strong feelings about steiner/sophiamundi from several years ago. I wondered if anyone has sent a child to steiner in secondary and would share their experiences. DD has ASD and while very bright is finding senior school competitive and stressful.
My friend teaches at one (not in the UK). It is a very caring and idealistic place. The children with SN are helped and supported in a much more organic way that at the last school she worked in. Part of the school's idealism is its concern with other aspects of education than passing exams.
Also, the school doesn't seem to suffer from the problems which I think often crop up at Steiner junior schools.
Good luck with your decision. No school is perfect, but I would certainly be interested in a Steiner secondary if one were available to me.