Dan Kois writes: “Kids in 3rd and 4th grade are beginning to stop reading for fun. It’s called the ‘Decline by 9,’ and it’s reaching a crisis point for publishers and educators. What’s causing the Decline by 9? It might be screens, but it’s not only screens. Indeed, several people I spoke to mentioned that middle-graders’ lack of phones created a marketing problem in an era when no one at any publishing house has any idea how to make a book a bestseller other than to hope it blows up on TikTok.