The dataset was a study from the 1980s where they had randomly assigned 12,000 kids to kindergarten classes. The kids are now about 30, and how much they learned in kindergarten (a proxy for teacher quality) was related to how much they earned at age 27. And kids with some teachers learned more than kids with other teachers.
All else equal, they were making about an extra $100 a year at age 27 for every percentile they had moved up the test-score distribution over the course of kindergarten. A student who went from average to the 60th percentile — a typical jump for a 5-year-old with a good teacher — could expect to make about $1,000 more a year at age 27 than a student who remained at the average. Over time, the effect seems to grow, too.
They say that 1 standard deviation in improvement in teacher quality raises students' annual earnings by 2.9%, so the incremental lifetime increase in earnings for a classroom of 20 kids from moving out a 25th percentile teacher and moving in a 75th percentile teacher is $320,000.
They looked at all the other things, like teacher experience and class size, and they had minor effects, but this one stood out.
If this scales with good teachers later on, quality of P-5 education could have an enormous effect on lifetime income. It is the educational version of the miracle of compound interest. You have more to build on for longer.
It's not an argument for paying kindergarten teachers $320,000 a year, but it is an argument for starting them at $50 or $60,000 and the good ones working up to $100,000 (or some numbers; I don't actually know how much we should pay them, just more).
And it is an argument for figuring out which teachers are good and which are not and either teaching them to be good or helping them find another career.