That doesn't line up though. See if you're 13 and meeting the level in 2012 your scores don't decline. So the levels would lag a few years. The 8 year-olds show up and miss the mark in 2017 that indicate the infinite scroll problem was having a toll on them.
Additionally this would start to show in class specific measurements (those kids with access to home internet, personal devices, etc. would have worse scores). I think the argument about social media has merit in discussion of children, but it seems more of a social distinction rather than an objective indicator for academic performance.