All teachers take five-year degree courses (there are no fast tracks) and, if they intend to work in primary schools, are thoroughly immersed in educational theory. They teach only four lessons daily, and their professional autonomy is sacrosanct.
"In Sweden," Sahlberg says, "everybody now agrees free schools were a mistake. The quality has not improved and equity has disappeared. If that is what Mr Gove wants, that is what he will get."
"Some would say it's the other way round: we have educational success because we have economic success.". The gap between high and low achievers is the smallest in the world and nobody talks of failing schools because there isn't that much difference between schools' results.
"Pisa is not what we are about. League tables are not a good measure of a school system. We never aimed to be the best in education, only to have good schools for all. Equity came before a 'race to the top' mentality."
Most pupil achievement is explained by factors outside of school authorities' control and that, if politicians wish to elevate children out of poverty, they should look to other public policy areas.
Finnish language is written almost exactly as it is pronounced.
Influences outside the schools are more important. Finnish adults, he says, are the world's most active readers. They take out more library books, own more books and read more newspapers than any other nation.
Exporting what appear to be educational success stories is a dubious enterprise, because it is so easy to misread how another country's system works and to discount its cultural background.
We need less formal, class-based teaching, more personalised learning, more focus on developing social and team skills.