Teaching is easier in England's secondary classrooms than in almost any other country, shocking new findings from the world's largest testing study revealed this week.
England outranked competitors - including Japan, the US, Russia and Australia, and many developing countries - in having "few limitations" on teachers getting on with the job.
But the findings were greeted with some scepticism this week. One leading academic described them as "unbelievable".
Secondary school maths and science teachers in 49 countries were asked whether there were any factors that inhibited their ability to teach effectively.
They had a list of possible "limiting" factors to choose from: pupil misbehaviour, children being "uninterested", and, more controversially, the presence in class of pupils with different academic abilities, special needs or disparate parental backgrounds.
Teachers' responses were compiled in an index, which shows that 64 per cent of England's maths lessons, and 60 per cent of its science classes, were conducted with "few or no limitations" on teaching.
This ranking left England second only to Scotland in maths lessons - 71 per cent of Scottish classes had "few limitations" - and Armenia for science lessons (62 per cent).
Only 5 per cent of England's science lessons, and 12 per cent of maths classes, were found to have many limitations on teaching.
Julian Elliott, professor of education at Durham University who has carried out study visits to classrooms in Russia and the Far East, said: "It's unbelievable. My experience of having talked to people from Asia, and having been out there and in Russia, does not correspond to this.
"If you took a classroom from England and one from Japan, I suspect the Japanese pupils would be better behaved."
Professor Alan Smithers, of Buckingham University, also questioned the results: "This may raise questions about the nature of the schools in which the surveyed teachers taught. Or it may be that teachers in other countries are looking at this question differently."
The survey was conducted as part of the Timss international testing study, which this week ranked nations according to the performance of their 10 and 14-year-olds in science and maths tests, with England achieving very good results.
The survey compared teachers' views on the number of "limitations" they experience with their pupils' test results and found that pupils working in classrooms with few limitations easily outperformed those with many.
In the primary "limitations" rankings, England was slightly further down the tables, but still in the top 10, out of 36 nations.
The main Timss findings saw England registering its best performance in international tests since 2000, improving strongly in maths and maintaining its position in the top seven nations in science.
Boys outperformed girls in three of the four tests, but the gaps were very small.
The results provoked a bout of soul-searching in Scotland, which finished below England in all four of the tests, and only in line with the international average.
Fiona Hyslop, Scottish education secretary, is calling a "top-level summit" of educationists and business people early in the New Year. She described the results as "alarming" and "completely unacceptable".
England among the elite in maths and science ratings, pages 18-21.