This claim is misleading as it blurs the line between kids and overall Americans. Yes, there is a 40% decline in reading, but this is measured from Americans 15 and older (as said in the article). The data-driven article provided is not speaking about children but instead mostly about adults. To add to this, the wording also suggests that this drop is due to cellphone usage, but the article suggests correlation, not causation. This makes the claim here feel more definitive than the science allows. What makes this misleading instead of false entirely is that the primary source is accurate and reliable.