The PA Consulting Group delivered a presentation called The Continued Economic Decline of the West where among other factors, presenter Jon Moynihan pointed out that the best of the high income countries invested more in teachers. The graph below shows the correlation between the comparative income a teacher earns in a country and the scores its students earn in the Performance for International Student Assessment (PISA). It shows that if a teacher earns more in relation to other careers in their country, their students perform better.
The Organisation for Economic Co-operation and Development (OECD) was quoted on this slide:
"In general, the countries that perform well in the PISA attract the best students into the teaching profession by offering them higher salaries and greater professional status."
Of course in the 'real world' there are budget constraints, but these high performing countries "tend to prioritise investment in teachers over smaller classes" according to the OECD. Therefore while having both quality teachers and small classes are the ideal, you should go for better teachers using pay as an incentive if you had to prioritise one over the other.
According to a study by Stanford University titled The Economic Value of Higher Teacher Quality, a teacher one standard deviation more effective than an average teacher generates $400,000 of extra annual income from a class of 20. That's $20,000 more per year for each student, just from having a slightly better teacher, nevermind the best.
We need to remember that like all professions, not all teachers are equal. Many are not committed and simply do it because they feel they have no other choice. In the end it comes down to pay. Sure, anybody that teaches and earns little money took the job knowing this from day one, but the problem is that there are too many not choosing the career at all. Teaching does not attract the best minds like it used to and this is because of pay. Of course there are still bright teachers, but just by looking at what the top students in any school are choosing to study, it is clear that most are bypassing teaching. Here is the simplest but most telling graph of all. It shows the percentage of teachers in America that graduated in the top third of their classes in 2012 compared to 1930.
While the burden of learning rests with the student, a country with high quality teachers will no doubt produce more top students who will go on to generate more value in their country's economy. A good teacher inspires, facilitates and leaves no student behind. To attract this calibre of person, the money and status given to teaching needs an upgrade in countries like the U.S.A and England.