Indeed, when the stats themselves say that between 1% to 14% of the students' mark was determined by the quality of the teacher. One has to wonder if as much time and effort was put into the other 86%. It brings back to mind a similarly minded statement made by my Uni stats professor; make sure you're measuring what you think you're measuring.
It seems very useful to know how much of the students' performance is up to the teacher.
If very little, than we don't need to worry about quality teachers, and just get the minimum level necessary to keep the peace in the classroom.
If a lot, then we should worry a lot about teacher quality, and work hard to make sure that we are only recruiting and keeping very effective teachers.
I know we love to harp on about teacher quality, but there are plenty of other factors that are just as important like access to the right learning programs, classroom mix and so on.
As a teacher I'll be the first to admit that for some students about the best we can hope for is to keep the peace until the mature or find something compelling that gives them a reason to succeed.
It's not as simple as "all teachers make $difference%".
I admit that I said that comment from a place of annoyance: during pay analysis, teacher quality matter a lot, and during results analysis, teacher quality doesn't matter.
But as you point out it's not uniform. It's reasonable that teachers make a big difference in some scenarios and not in others.
