Beliefs that are debatable or even patently false may be repeated so often that at some point they come to be accepted as fact. We seem to have crossed that threshold with the claim that U.S. schools are significantly worse than those in most other countries. Sometimes the person who parrots this line will even insert a number -- "We're only ____thin the world, you know!" -- although, not surprisingly, the number changes with each retelling.
The assertion that our students compare unfavorably to those in other countries has long been heard from politicians and corporate executives whose goal is to justify various "get tough" reforms: high-stakes testing, a nationalized curriculum (see under: Common Core "State" Standards), more homework, a longer school day or year, and so on.
But by now the premise is so widely accepted that it's casually repeated by just about everyone -- including educators, I'm sorry to say -- and in the service of a wide range of prescriptions and agendas, including some that could be classified as progressive. Recently I've seen it used in a documentary arguing for more thoughtful math instruction, a petition to promote teaching the "whole child," and an article in a popular online magazine that calls for the abolition of grades;(following a reference to "America's long steady decline in education").