This is not time-series data. The study design here (a cross-sectional survey of varying countries, showing a bare correlation between two variables) is not adequate to show causation.

http://norvig.com/experiment-design.html

(By the way, the scatter of data points around the regression line in their plot suggests that the model is subject to large degrees of error in prediction.) It would take an experimental design (randomly assigning one group of teachers in the same country to receive pay raises while another group does not, with before-and-after comparisons of pupil performance) to show that paying teachers more results in higher pupil performance.

http://escholarship.org/uc/item/6hb3k0nz

There have been hundreds of studies of educational interventions over the years,

http://www.amazon.com/Visible-Learning-Synthesis-Meta-Analys...

and many thoughtful international comparisons of teaching practice,

http://www.amazon.com/Teaching-Gap-Improving-Education-Class...

http://www.amazon.com/Knowing-Teaching-Elementary-Mathematic...

http://www.amazon.com/Making-Learning-Whole-Principles-Trans...

but none of those conclude that simply raising teacher pay, without changing teaching practices and perhaps also the composition of the teaching workforce, will have much to do with raising pupil performance in any place. Raising teacher pay systematically has been tried in the United States (notably in the state of Connecticut) and has not been shown to markedly raise pupil performance.

An economist who closely studies education policy has suggested that pay and other incentives be used to encourage the least effective teachers to seek other occupations while rewarding the most effective teachers with increased compensation and more professional support.

http://edpro.stanford.edu/hanushek/admin/pages/files/uploads...

Such a policy, he estimates (showing his work in his article) would raise United States educational achievement to the level of the highest-performing countries. This is something worth verifying by experiment, although that will be politically difficult in any state of the United States

http://www.cato.org/pubs/journal/cj30n1/cj30n1-8.pdf

and perhaps in Britain as well.

http://www.economist.com/node/17849199

P.S. I'm curious about why the United States underperforms so much compared to salaries paid to teachers in the chart shown in the submitted blog post.

Visible Learning, by John Hattie

http://www.amazon.com/Visible-Learning-Synthesis-Meta-Analys...

Teaching as Leadership, by Teach for America

http://www.teachingasleadership.org/

http://www.amazon.com/Teaching-As-Leadership-Effective-Achie...

Understanding Numbers in Elementary School Mathematics by Hung-hsi Wu

http://www.amazon.com/Understanding-Numbers-Elementary-Schoo...

Most of the achievement gap actually comes from parenting, not schools.

John Hattie in his book Visible Learning: A Synthesis of Over 800 Meta-Analyses Relating to Achievement

http://www.amazon.com/Visible-Learning-Synthesis-Meta-Analys...

reviews a lot of research studies from a lot of countries and suggests that that view, although it is conventional wisdom, grossly underestimates the importance of schools. I agree with you, because the data agree with you, that the most stark differences in school performance are among different teachers in the same school rather than between one school and another, but throughout the Western world, students with tough home conditions tend to get the lousiest teachers and the most underperforming curricula.

Other writers who have important points to make about how to help learners with the worst home environments by improving schools include the collaborators from Teach for America who have put together the book and website Teaching as Leadership

http://www.teachingasleadership.org/

and Eric Hanushek at Stanford with his research on the effects of variance in teacher quality.

http://edpro.stanford.edu/hanushek/content.asp?contentId=60

There is a lot yet to be done that is very feasible (well, except for politically feasible in most states of the United States) to improve the education of the most disadvantaged learners and to help them reach significantly higher levels of academic achievement.

The evidence suggests that . . .

Citation, please? I'm reading a very good book about evidence for best practice in education,

http://www.amazon.com/Visible-Learning-Synthesis-Meta-Analys...

recommended to me by a candidate in the current school board race in my school district, and I'd like to check what the research says with any source you recommend.

Do you have any evidence for any of other assertions in your comment? I will look it up if you would kindly provide citations.