What was the reason your DD was put into the year below when she did eventually start school? I would have thought that regardless of whether children are kept at home (e.g. Home Ed) for a period of time they would, on going to school, be put in an age appropriate class. It sounds as though someone didn't check DOB's? or there was a particular reason? Was she premature and should have been born in late Sept / Oct?
Regardless of ability at 6 when she went to school, I would have thought she would have been placed in an age appropriate class.
Sorry I don't know the rules on 11+, but yes, as others have said, speak to the school, LEA.
There are students in the wrong years at grammar, both up and down, for a variety of reasons. Placed ahead in primary, educated abroad etc.
I deliberately chose for my DD not
to be in what you call 'an age appropriate class' , ie she was the oldest in the class rather than one of the youngest. This was the big battle - keeping her out of school was relatively easy; making sure she then didn't just get put into Year 1, thereby missing Reception, was much harder. It w very important to me that she wasn't just slotted into the year I had fought to keep her out of. However, what we did was miss out year 2 entirely and she went from year 1 to year 3 as she had matured a lot by then. And then she missed out year 4...
None of it did any harm, and I reckon it did lots of good.