Charlotte Iserbyt wrote a big book on this topic - The Deliberate Dumbing Down of America. She worked within the federal education institution during the Reagan years before becoming a whistle blower. Her web site promotes this book but also includes some sample passages you may find interesting, I think maybe the entire Preface.
PS - after posting the link, I went to this site just to confirm the information is still there. I see she is now offering the electronic (PDF) version of the book for free, which tells me she really wants to get the info out there.