Does Shanghai's school success exclude migrants?
Could China really hold valuable lessons for England's education system?
After a day in Shanghai visiting schools and talking to teachers and pupils, Education Minister for England Elizabeth Truss is convinced.
"First of all it's the attitude," she said. "There's a strong belief that maths gets you everywhere, that it's a really important subject and that everyone can achieve in maths."
"Secondly, I think it's the focus on the core basics, making sure that every student gets arithmetic and that they can do their times tables and their long division."
Shanghai has now twice topped the Programme for International Student Assessment - or Pisa - league tables, run by the Organisation for Economic Co-operation and Development.
The Pisa results show that in maths ability, by the age of 15, Shanghai students are three full years ahead of their British counterparts - and that is why the UK delegation are here.
Even much younger children are streets ahead, it seems.
The UK government press release accompanying Ms Truss's visit gives examples of the kind of questions the city's eight-year-olds are expected to answer.
For example: "Thirty-two different football teams entered the 2006 World Cup. Every team had 23 football players. How many players in total were entered in the World Cup?"Missing students?
But not everyone is so sure that Shanghai offers much to emulate.
Research published by Professor Tom Loveless at the Brookings Institution, a Washington based think-tank, suggests that Shanghai's strict residency rules mean a huge number of the most disadvantaged students are missing from the Pisa figures.
A city of 23 million people should, according to the global average, have almost 300,000 15-year-olds.
But Shanghai has only a little more than 100,000. In other words, many thousands of 15-year-olds appear to have vanished into thin air.
These are likely, he claims, to be the sons and daughters of Shanghai's huge migrant population.
Such migrants can live for many years in Shanghai, in low paying jobs, but never be given the full residency status, or hukou, that entitles their children to attend high school.
This, Mr Loveless says, makes the Shanghai data useless as a comparison with other education systems.
Its Pisa test scores are likely to be artificially inflated because such a large number of the most disadvantaged students are missing.
And it makes a mockery, he says, of Pisa's claim that the Shanghai results show the city to be a model of educational equity.
A claim repeated in the UK press release: "During this visit," it says, "the group will particularly be investigating how the performance of almost all children in Shanghai is high - irrespective of gender or income, for instance."
Pisa refutes much of Mr Loveless's analysis, pointing out that it does have migrant students in its sampling.
Lu Jing is deputy director of the Shanghai Institute for Basic Education Research and the national project manager for the Shanghai Pisa team.
She says that 26% of the students sampled in the most recent tests were born, or had parents who were born, outside Shanghai.
"Every country is the same," she says, "and Shanghai is not allowed to exclude certain groups of people."'It's the system'
So what is the truth? Well, it is certainly easy to find excluded students in Shanghai.
Fourteen-year-old girl Deng Yue has lived in Shanghai with her parents, migrants from Jiangxi Province, for nine years.
But because they do not have a Shanghai hukou she is about to leave the city to travel hundreds of miles to their former home town to attend high school.
"There's nothing we can do," her dad says. "My daughter doesn't want to leave, but it's the system."
And while there are migrant students in Shanghai's schools, these are likely to be the ones whose motivated and educated parents have managed to fulfil the points-based residency requirements.
There is no doubt that a visit to any Shanghai school will leave you impressed.
They are full of motivated and diligent students, the city has been investing in educational hardware and the teachers and parents are engaged and passionate.
You cannot blame anyone for wanting to try to bottle some of that and bring it back home to their own school systems.
Members of the UK delegation tell me they have been particularly impressed with the Chinese diet of early morning maths lessons and the obligation on teachers to mark and return homework the same day it is submitted.
But critics warn that beyond such details, Shanghai's educational system cannot be separated from the context of the Communist Party's population controls and the deeply unequal society it governs.