I recently heard this from someone. Does anyone have a link to the recent research indicating this? My reflex is to be immediately suspicious of narratives along the lines of "everyone is stupid," especially in online communities with fringe political beliefs.
The whole part trying to dodge the correct allegation that the US ranks 125th out of 195 countries is really depressing. "Uhm actually, there are some variables that are skewing these results.*"
*Variables that are skewing the US to rank higher than it should.
I think the "6th grade" bit is made up to help translate the results of these studies into something even 6th graders can understand, but the feds do these massive studies every now and then