The performance of Mexico's private schools, where the vast majority of the nation's middle-class is educated, declined from 2008 to 2009 in the Prueba Enlace, the most important annual grade-school exam. The number of students deemed "good" and "excellent" in Spanish and math declined this year, while the proportion of students in the unsatisfactory range ticked up in math and spiked from 9 to 12 percent in Spanish.
My own very unscientific opinion is that students, especially those from the middle class, enter middle school with more developed social-networking skills with every passing year, and this has a devastating impact on proper written communication. Of the twelve-year-olds I teach, the overwhelming majority (I'd guess around 75 percent) use IM programs, Facebook, et cetera, on a daily basis, which of course has much less formal strictures regarding proper writing. Most of these students have been using such programs for several years, and for many, the spastic online idiom is their de facto writing style, even when they are not on the computer. Needless to say, always writing K instead of qué or amiiiigooooo instead of amigo or TQM!!!!! instead of ¡Te quiero mucho! isn't conducive to effortlessly picking up the finer points of written Spanish.
Nonetheless, the private schools' performance remained significantly better than the public schools.