Let's be clear: both explanations are that higher salaries result in better teachers which in turn results in higher student performance. It's not that saying that paying a teacher more results in higher performance.
A lot of teachers do this, from kindergarten to high school. I've had to hang out in a educational supply store more than once in my life when I and <pick any friend that is a teacher> have passed by one. That teacher then blows a sizable chunk of coin without fail.
Arts & crafts, books, lined paper, sci calculators, and of course... stickers for that job well done.
In my experience, schools in the US actually waste a huge sum of money because they have incompetent administrative staff (with the added bonus that they're overpaid).