Years ago, I read a journal article on the dumbing down of the texts kids read. I'm not sure if this is the same one or not:
Schoolbook Simplification and Its Relation to the Decline in SAT-Verbal Scores (pdf)
The article talks about two specific movements to simplify the language of children's school books. The thinking was that kids needed the content, and by simplifying the language, they could access the knowledge more easily. The problem was, by dumbing down the texts, they never taught kids how to read more-complicated things. According to this study, only high school science books are written at a level above the level of newspapers, everything else falls below.