Help I am not sure whether I made the right choice for our DD by going to our local comprehensive

Are you sure the target is based on the Cat tests? Usually school use these tests to set the children. GCSE target grades are based on their KS2 Sats results via the DofE, I didn’t think school were allowed to set target grades themselves?

As she is happy I really wouldn’t worry and would keep here where she is settled.

I've no idea if this is the case by the way but...is it possible the school are measured on how many children exceed their target (and how many children fail to achieve it) so this incentivises the school to predict a lower grade then they otherwise would so the percent of children who out-petform is high?

If your daughter is happy and settled at her school and has a good friendship group then I wouldn’t move her. I would probably get her a tutor a couple of times a week, one in English and one in Maths and then maybe switch up subjects as she gets older.

I don't really work in educational research any more (though I do still follow it from personal interest). Unfortunately, some of the more detailed studies are only open to people working in the field, but if it's a subject which interests you, there is some basic DoE research.
The CSPAR study is also worth a look.

It's quite hard to quantify the impact of various elements of the school process because they are interlinked, so isolating one factor and stripping out relating issues is not a perfect science. But the DoE paper references several earlier studies which haven't found a definitive link between class size and attainment (at secondary level, they might show a benefit at primary level) and others which reiterate the beneficial impact of good teaching. HTH

I have pm’d you @daysem

The advantages of small class sizes is often overstated @daysem. Conversely the impact of great teachers is often understated (and no, I'm not a teacher!).

Most of the pedagogical research actually shows that the quality of teaching is a considerably more significant factor – so DCs do better in large classes with a good teacher than they do in small classes with a poor one.

Of course, there are exceptions to this general rule, before anyone goes all anecdotal on me, but that's what the data shows.

Ds1 was average, based on his SATs and CATs they placed him at a predicted flight path through school to achieve a 4/5 in English lang and a 6 in maths.

They supported and nurtured him. At home we widened his knowledge base on things they were covering in school, so for Geography they covered the Grand Canyon so we watched a couple of videos on YouTube from the National Parks who oversee the Grand Canyon. We did this alongside learning things just for fun. The internet and especially YouTube is a great resource. We played games together, watched tv shows and discussed Ross's relationship with Rachel in Friends etc etc. Learning isn't just about something you are tested on.

When it came to year 9 Ds started to get confident in his ability because he was now doing the option subjects he liked. He decided that his grades predicted from when he was 11 years old were not going to define him. He put in a little bit extra effort at home, genuinely not a huge amount and saw him achieve a grade 8 in English lang and a 9 in maths. The majority of his GCSE grades were 9s.

Life is not defined at 11 or 12. Learning is not linear. All the CATs do is give school a baseline so that they can show Progress 8 information. Learning doesn't just take place in school. Your role as a parent is just as important, supporting homework, showing an interest in what they are learning about. We never asked did you have a good day but instead my children came home and said in maths we did angles, in History we did Catholic threats in Elizabethan society etc. These things can spark conversations with them also teaching you things too.

The school has a good reputation, I would keep her there and see how she gets on. Money can be spent on tutors rather than independent schools. Also you may wish to just look at how much it may cost you to support a child going through university. You might want to save for that www.savethestudent.org/student-finance/maintenance-loans.html

Yes we had the same for ds1. We decided to keep him in the secondary school and just pushed him at home and used the money we saved to stretch him in other ways like tutors and travelling.
If you can afford it comfortably then I would choose the independent school.

Setting a target of 6+ does not mean that that they do not expect her to get higher, or that they will not push her to do so.