I can think of a few reasons why teacher salaries are low, at least on the US side not sure why its high in this chart, particularly in the public school system and not in private ones. Most teachers work about 6 hours instead of the average 8 hours a day, and they don't work in the summers unless they teach summer school, other part time jobs, or work at a school that offers year-round education. There's also economic and political pressure that can lead to budget cuts, so even if there's some high salary that does not necessarily mean it will last.
I can think of a few reasons why teacher salaries are low, at least on the US side not sure why its high in this chart, particularly in the public school system and not in private ones. Most teachers work about 6 hours instead of the average 8 hours a day, and they don't work in the summers unless they teach summer school, other part time jobs, or work at a school that offers year-round education. There's also economic and political pressure that can lead to budget cuts, so even if there's some high salary that does not necessarily mean it will last.