Between 1939 and 2009, human ingenuity has invented a lot of new things one can do with one’s time. Human ingenuity has not, however, invented a method for stuffing more hours into the day. Consequently, if you look at just about anything that people could do in 1939—read for pleasure, take care of children, cook, etc.—they do somewhat less of it in 2009. People who are really into books, or cooking, or natalism, or what have you tend to interpret this inevitable crowding of the timespace as a sign of cultural crisis and decline but it’s an inevitable result of heterogeneous preferences and innovation.
I feel that's about right. There's nothing particularly special about "books" or "classical music" or "theatre" that sets these apart from other media or cultural productions. Sure, they all have their strengths, but this means that we're all better off for having tons of options for consuming information and media. Maybe kids can't translate Latin or whatever as well as they used to; but that's inevitable as something has to give way as they pick up other skills and talents suited for today. Instead of worrying about how to force high school students to read things they aren't prepared to understand, schools should instead focus on how to introduce kids to a broad variety of media that they'd find interesting and accessible.
Twitter, however, is one social medium too far. It really is the sign of cultural decadence.