The most successful schools ignore government advice and set their own standards for effective teaching, according to a thinktank report published today.
The best schools have an "open culture", in which heads regularly pop into classrooms informally, the thinktank Reform says.
"The teachers view this as supportive rather than threatening ... the best schools foster an expectation and culture of perpetual improvement."
This change in culture leads to failing teachers either improving or leaving, the report says.
Being taught by a good teacher rather than a poor one improves a student's results by half a GCSE grade a subject, according to academic research quoted in the report.
By contrast, class size makes little difference.
Korea and Japan, which have bigger class sizes, do better at maths than pupils in England, according to Organisation for Economic Co-operation and Development (OECD) figures.
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