Many studies, for example the 2007 McKinsey Report (“The quality of an education system cannot exceed the quality of its teachers”), suggest that teachers matter more to students’ achievement than any other school-related factor.
However, in the context of social mobility, we would like to know whether teachers also affects the long-term outcomes of their students. Using big data gives us now the tools to analyze and identify factors that facilitate or hinder social mobility, among them school factors such as the teachers and the educational environment.
One way to measure teacher quality is by the “value-added” (VA) approach, which rates teachers according the improvement of their students’ test scores. Which raises the question: do high-VA teachers have an impact beyond the school years – on college attendance, future earnings and so on?
Answering this question can shed light on broader issues regarding educational interventions. It will help us to assess the economic return on investment in better teaching, and to know whether a change in test scores is a reliable indicator of programs’ long-term impact.
A ground-breaking study in the US examined this issue using a huge database for more than one million children. This data included their test scores in math and reading in grades 3-8, as well as records indicating their social and economic situation as young adults, up to age 28.
The researchers found that even one school year with a good teacher had a significant effect on the children’s future in different aspects. Students assigned to high-quality teachers were more likely to attend college and earn higher salaries, and less likely to have children as teenagers.
Another interesting finding, especially in view of the difficulty recruiting and retaining excellent teachers, is that the difference in impact between an average and a weak teacher is similar to the difference between a good teacher and an average one.
The calculation of the teachers’ impact over time will give you an idea of its significance: replacing a very weak teacher (VA is in the bottom 5%) by an average one for one year would increase the lifetime income of a 30-student class by an estimated $250,000.
So where do we find better teachers? Our experience shows that with intensive pedagogic training, teachers can lead students who failed in the past to achievement. This is applied in programs such as Start, where students who were at risk of dropping out graduate high school with a matriculation certificate – a key to higher education and social mobility.
