How about an elephant standing between the teacher and the student, being that unmentionable "60%" influence of families?
Between poverty and negative/unsupportive home environments, teachers and the education system are constantly trying to undo the damage done by the student's return to those negative environments every day from K-through12.
I think that was a high-leverage point that Jack was pointing to.
The opportunity to scapegoat teachers appears to be an agenda to eventually convert public education into a for-profit corporation driven enterprise, just like the US health care system. By focusing everyone's attention on low-leverage points that will not resolve the problem the public system can be attacked knowing full well the problem will not be fixed, thereby enabling the "privatization option" as the only solution on the table.
The public debate appears to have very little to do with educating all students.