The top 10 per cent of teachers are twice as effective as the bottom 10 per cent, according to this paper.
The research, by ANU economist Dr Andrew Leigh, differs from previous Australian studies in that it uses a measure of teacher effectiveness based on test score gains, not levels.
Using a dataset covering over 10,000 Australian primary school teachers and over 90,000 pupils, Leigh estimates how effective teachers are in raising students’ test scores from one exam to the next. Since the exams are conducted only every two years, it is necessary to take account of the work of the teacher in the intervening year. Even after adjusting for measurement error, the resulting teacher fixed effects are widely dispersed across teachers, and there is a strong positive correlation between a teacher’s gains in literacy and numeracy. Teacher fixed effects show a significant association with some, though not all, observable teacher characteristics. Experience has the strongest effect, with a large effect in the early years of a teacher’s career. Female teachers do better at teaching literacy. Teachers with a masters degree or some other form of further qualification do not appear to achieve significantly larger test score gains. Overall, teacher characteristics found in the departmental payroll database can explain only a small fraction of the variance in teacher performance.