While standardized testing, merit pay for teachers, and removing union power all play a role in education reform, these factors pale in comparison to the status of teachers. If teaching is a high status profession, young graduates will flock to it.
In the US, it is not a high status position and our elite college graduates rarely enter the field. Contrast this with Japan, where teachers are considered high ranking members of their community and are even called by the title sensei (also used for doctors).
Here’s the story in Finland (it started with legislation):
The second critical decision came in 1979, when reformers required that every teacher earn a fifth-year master’s degree in theory and practice at one of eight state universities—at state expense. From then on, teachers were effectively granted equal status with doctors and lawyers. Applicants began flooding teaching programs, not because the salaries were so high but because autonomy and respect made the job attractive. In 2010, some 6,600 applicants vied for 660 primary school training slots, according to Sahlberg.
From Smithsonian Magazine
I don’t understand why this story is so rarely covered in the press. It seems to be the most solidly proven factor behind the success of the world’s best education systems.