Teacher training programmes vary enormously and are evaluated rarely.
Most consist of theory at a university followed by a short in a school.
Graduates consistently report that the taught them almost everything they use.
That finding has survived in every country where it has been studied.
Reform has therefore extended school-based training, with mixed results.
A is only as good as the teacher it.
Where is unpaid and unrecognised, it is delegated to whoever cannot refuse.
Systems that pay for mentor time and train the mentors show measurably better .
is the second contested area.
Primary teachers in many systems have studied little mathematics since school themselves.
The evidence suggests that what matters is not advanced knowledge but knowledge of how the subject is .
A teacher who can predict the wrong answer teaches better than one who only knows the right one.
This kind of knowledge is specific, teachable and largely absent from degree courses.
Continuing development after is weaker still.
Most of it consists of one-day events, which the research has shown for thirty years to change nothing.