@NobleGiraffe
Re: "I think you must be reading different figures. The overseas acceptance rate that I saw was 14.2% for Cambridge. The under-18 acceptance rate was 11.9%. Even if the vast majority of under-18s are from overseas, it does look like youngsters are less likely to be accepted than 18 year olds."
I looked at 5 years from 2013 - 2017. Here are the most recent 5 years including a 95% confidence interval for the under 18's (since these have the smallest numbers and are therefore most prone to statistical fluctuations).
year Overseas Under-18 95%_CI
2017 14.2% 11.9% _ 9.3% - 14.6%
2016 12.3% 10.2% _ 7.7% - 12.6%
2015 12.5% 10.2% _ 7.7% - 12.6%
2014 12.1% 14.8% _ 11.8% - 17.7%
2013 11.9% 12.5% _ 9.6% - 15.4%
In 2 of the 5 years, the under 18 acceptance rate was actually higher than the overseas rate. In all 5 years, the confidence interval for the under-18's contains the overseas rate, i.e. the hypothesis that they were different would be rejected. In short, there is no significant difference between the under 18's rate and the overseas rate, and therefore no evidence that age was a significant factor.
"Given that these youngsters have been accelerated because they are supposedly fantastically brighter than the surrounding population, you’d expect the acceptance rate to the top university for maths to be higher than the norm. Unless their age or education was a disadvantage"
This is a logical non sequitur. Just because someone makes an early application to a university does not mean they are gifted. There is no information about their ability level and therefore no conclusion can be drawn. Your argument is essentially: some gifted students apply early to university, these students applied early to university, therefore they must be gifted. It's the same logical fallacy as: Socrates likes logic, I like logic, therefore I am Socrates.
This is in any case a distraction from the fact that UK universities, including the top ones like Cambridge, take students under the age of 18 in fairly large numbers - they are not overwhelmingly hostile to this practice as you contended.
"So this advice is: radical acceleration, early entry to your local ex-poly, and it will be fine because it worked out in the long run for someone from Victorian times?"
That is a gross distortion of what i have said.
- BertrandRussell's statement was that early entry was not ever appropriate. I cited a counterexample of an eminent mathematician who went to Harvard at the age of 11, did groundbreaking work by the age of 17 and subsequently had a long and successful career. The point being that if we acknowledge that there are any cases where it is appropriate, the next question should be: how many?
- The evidence in favour of radical acceleration comes from multiple studies involving thousands of participants. The international review of research by Gross was published in 2005, the meta-analysis of Moon et al I previously linked was published in 2011 and was based on 38 primary studies conducted between 1984 and 2008, so to suggest the evidence in favour of acceleration is in any way dated is not justified.
- You have yourself acknowledged that many schools barely have the subject specialists, expertise or resources to teach even the standard A level curriculum. The places that do have the expertise to teach beyond this level are universities.