[rahimnathwani]

  Productivity in what sense?

If I told you I would give you either $27k to spend as you wish on education, or let your kid go to a SF public school (which would spend the $27k as it seems fit), which would you choose? I'd pick the former.

  if large swaths of the workforce were illiterate

I live in one of the richest cities in the US. Here, about 50% of 11th graders attending public schools can read and write at a level that meets the minimum state standards (which is a low bar).