The 11+ was a eugenics test to weed out genetically "inferior" children, created by a classicist who falsified his research

did you read more than the abstract on both article? Because the research does say that there are benefits to selection but that it may not be worth the negative consequences to the remaining state schools.
not behind a pay wall and more recent this will be of interest to you.
Consequences of academic selection for post‐primary education in the United Kingdom: A systematic literature review - Cantley - 2025 - Review of Education - Wiley Online Library
Not only better grades but higher wages unfortunately it entrenches lack of social mobility. But statistically significant advantages to selection.

DS is in Year 7 at a superselective grammar school. He has already been to Astronomy, Physics and all sorts of academic extension clubs and talks given by former pupils who return to discuss eg their PhD they are doing at Cambridge and specific research products they have been invited to. I never told DS to go, he really wants to! Most of his former primary school friends would have zero interest in this kind of thing.
The local comprehensive offers none of this, albeit much larger, the kids are more interested in sports there and other types of clubs like wood work. DD is also in a superselective grammar and going to a lecture at LSE and I think another talk at UCL just next week and a number of her year group are going along. It is open to everyone but the kids in these schools are interested in this stuff. It is not because they were overtutored or because the parents are “pushing” them. You do not push at Sixth Form, they do want they want! In fact, even in Year 7 you are not there to tell them which clubs to go to.

GCSE results are only part of the picture, a small one at that. The schools do not have extra funding to put much on. It is done by the students. They decide who to invite. When they eventually go along to their Oxbridge interviews they have lots to talk about, it is a natural consequence of years of this.

My Dad came from a very working class background passed the 11 plus in the 60s and went to Oxford with a full grant. There is absolutely no way he would have had those opportunities without the 11 plus the family wanted him to go into bricklaying like his Dad. It’s different these days though as most of the kids sitting the 11 plus have been tutored for several years at great cost to their parents

Sure. But my point is that a comparable environment can be achieved in a good comprehensive which has a diverse intake, then divides kids by ability over time.
A good well rounded comprehensive is an ideal to work towards. The concept might be worthwhile exploring but that's not what you are deep diving into on this thread. Currently I see schools that are often too big, overstretched with students on every end of the extreme; barely reading to ready to take on university texts, dysregulated to experienced at self study. I have family that live in a corner of Lambeth which is very much an inner city melting pot and not at all reflective of the general UK population it is overwhelmingly a deprived area of new immigrants with a smattering of very wealthy, not an area with a robust middle.

Can you deny that the 11+ test was created by an advocate of eugenics who falsified his research?
I don't think it matters who created this or how flawed the research, it is a remnant of the post WW2 ideology (and he wasn't the only person who held similar views or tweaked the data), obviously the exam itself has evolved and the questions are not the same as the questions asked in 1946 but part of the reason the exam remains is history, which I posted about earlier. Very few went on to post secondary and most went directly into a workforce and workplace of manual labor exiting school ready for employment at 16.

Can you deny that, regardless of the creator, there is still no scientific backing for the test?
https://www.nature.com/articles/s41539-018-0019-8 Here is some research that might interest you and would back up why it's a helpful tool.

Can you show the scientific evidence for why 10 is an appropriate age to test kids?
Honestly kids are continuously tested. It really doesn't matter when you test them. In your view children in a good comprehensive school would be regularly tested (paper or otherwise) and equally moved (albeit not a different school, simply different classes). Children are tested upon entry to reception, then tested with phonics, and then continuously assessed thereafter, lots of testing reported on mn during year 7.

I dodged away for a few days but have been reading along. @CatchingtheCat raises fairness as a stumbling block and the OP suggests that the 11+ is not the same nationwide. Plymouth and Torquay have grammar schools, for which the intake is the top 25% or 250 per year of the 11+ filtered cream. We also have, in east Devon, Colyton Grammar which selects only the top 7-10%. The best Exeter junior schools (both state and private) know they will lose their cleverest students to Colyton at 11, if they really are clever. It's quite straightforward. Clever parents breed clever kids, and so Colyton is a bit of an aberration socially.

You haven’t produced any evidence about how effective the 11+ is though. You have said it isn’t highly correlated to GCSEs and you have produced a couple of studies (I didn’t click through to unknown links but taking your c&p paragraphs at face value) about the grammar versus comprehensive system not an assessment of the 11+. If you provide normal links I will look at the results of your peer-reviewed studies (conclusions are always the authors’ spin, it is the results that are important, especially when the conclusion uses words like ‘imply’).

An important phrase for you to consider is “confounding variables”.

I have described how a study could be designed to assess the effectiveness of the 11+, though admittedly it would take five years to give a result.

What it comes down to though, it not about effectiveness of the 11+ or grammars vs comprehensives. It is whether you think it is FAIR. Something the education system quite patently is not, regardless of the 11+.

I am saying it is not possibly to determine whether the 11+ is a good selection test from the studies.

By way of context, I do not live, and have never lived, in a Grammar school area. I did go to a poor comprehensive though - probably as ‘true’ a comprehensive as you can get as was the only one in a small town with a very mixed demographic of wealthy and deprived areas. You could tell which were the wealthy areas by seeing where the vast majority of A level students lived.

It Is reasonable to compare grammer school system to the comprehensive system, but not to draw any conclusions about the 11+ as a selection test from that. There are too many confounding variables.

For your next task, you could consider whether a high UCAT score makes a good doctor….

If you want to determine whether the 11+ is a reasonable selection test then comparing the 11+ to GCSEs is not the relevant comparison. A relevant comparison would be to randomly allocate half a cohort to the 11+ selection criteria and half to some other form of selection criteria and seen which group get the best outcomes in terms of GCSEs, or some other more useful societal outcome measure than GCSEs, at the schools attended by both those selected for grammar and those not.

Or we could compare outcomes of grammar to comprehensive systems in children with similar demographics. But that would not be an assessment of the 11+

Do you mean 51% achieve better than under a comprehensive system and the rest achieve the same?

if 51% of the cohort gets a "better" result, that works for you, and the 49% for whom it didn't work can suck it up?

As opposed to what? You have not given the comparator.

But the lowest 30% is not a uniform group. There will be those unable to work or do so without a lot of support. Those who struggled at school for other reasons (eg family circumstances or ill health) who still have the potential to succeed academically, and a lot for who a bit more focus on them in school would give them grades access courses at college. Plus there is learning for learning sake; to have a better understanding of the world about us, to be able to better assess and critically appraise information they receive, to be better able to advocate for themselves (including in writing), to better compare financial products or quotes for services, to give their own children a boost in learning.

I do not follow. What criteria do you use to assess whether a test is valid or not? Note: "it worked well for me or my child" is hardly a scientific criterion

Whether it gives better results for the whole cohort (including both those who passed and those who failed or didn’t take the test) in adulthood or not.

You make these kids sound like a resource to be exploited for their talents. Maybe they don't want to do it. Maybe they have no idea in fact what they want to do as their parents have not listened to them but pushed and pushed for them to do science, maths etc.

I have a friend who decided that her son should be an actuary because it is so well paid and this boy was brought up with the goal of studying actuarial science at uni and he hated it and now teaches tai chi.

No, they just get paid the same as an adult in their work. (Sometimes they can be paid less as a vocational/training position, which o don’t think is quite right)

What I am saying is that SATs and the Kent test are in no way comparable. Do you understand normal distribution ? SATs are insufficiently sensitive for those DCs more than 1SD from the mean as they wil pretty much all get 100%. The Kent test has a great senstivity at the higher end and very possibly less at the other end. So yes some DC will do well in SATs but not achieve a good enough score in the Kent test to attend a grammar, even more likely if SS. I very much doubt it happens the other way with grammar school DCs who didn't do well in their SATs ( possibly some prep schools who do no prepartion for them).