It's a chicken-and-egg problem, as if you spend some time on an undergraduate campus in the US, you'll notice that majority of those majoring in Education have deemed other, more profitable, majors as too hard.
Finland has free college education. Mainly for that reason, the future profitability of a specific discipline doesn't appear to be a major factor in how young Finns choose their majors (as evidenced by the enduring huge popularity of objectively unprofitable disciplines such as media and design).
It seems to me that those that become teachers in Finland have chosen the career fairly early on. It's a vocational thing. Money doesn't influence the decision, but of course there is the financial baseline that teaching is a stable job that offers an extraordinarily long summer vacation (something like 11 weeks, fully paid).
Wow -- that alone could cause a number of the effects we're talking about. Anyone who wants to go to college can, versus in the US, there are a number of children who know (or pessimistically assume) that college is just not in the cards for them.
Not saying we should adopt that single tenet. Just that it has surprisingly strong ripples throughout the whole system that should not be underestimated.
