These are the top twenty countries with the supposedly 'best' education systems in the world:
Finland
South Korea
Hong Kong
Japan
Singapore
UK
Netherlands
New Zealand
Switzerland
Canada
All of them are much small countries, as far as population, than the US. Most of them are also very homogenous populations. Both of those things make it much easier to educate young people.
I don't know exactly how the UK got in this list, but I have a fairly good idea. I don't think it belongs there because I am quite familiar with the UK and the results of their education system in the sense of knowing very well many, many people from the UK and traveling there extensively.
I also know some very specific things about the education system and goals in the UK. In the UK system of education, students are taught to pass tests, not to be 'educated,' not in the sense of developing their intellect, developing their minds, being creative and critical thinkers, etc. Once they have passed those tests, most of that 'knowledge' is forgotten. That is what standardized testing is all about. It is not an indicator of how well developed one's mind is but how well one has been taught to pass a test.
I would not want my child to go to an average school in the UK anymore than I would want him or her to go to an average public school in the US. They simply are not any better in the UK, other than that they are better at cramming information down the kids' throats so they can do well on exams.
The problem with eduation in the US is not about money, it is about social problems. Schools expend about 50% of their energy, effort and money dealing with social problems rather than on actually educating the children. That is the problem that needs to be dealt with.