From my experience as a secondary school teacher, it's the latter which then leads to the former. Kids can't read. I'd say in my last year teaching I probably only had three kids who I would consider literate, able to read and make inferences, think about the material they're reading, etc. There's several reasons for this (and not just social media -- they're often taught to regurgitate for the state exams), but it's a real issue.
