Several significant studies of literacy have appeared in recent years showing just how low literacy rates were in antiquity. The most frequently cited study is by Columbia professor William Harris in a book titled Ancient Literacy. By thoroughly examining all the surviving evidence, Harris draws the compelling though surprising conclusion that in the very best of times in the ancient world, only about 10 percent of the population could read at all and possibly copy out writing on a page. Far fewer than this, of course, could compose a sentence, let alone a story, let alone an entire book. And who were the people in this 10 percent? They were the upper-class elite who had the time, money, and leisure to afford an education. This is not an apt description of Jesus’s disciples. They were not upper-crust aristocrats.
In Roman Palestine the situation was even bleaker. The most thorough examination of literacy in Palestine is by a professor of Jewish studies at the University of London, Catherine Hezser, who shows that in the days of Jesus probably only 3 percent of Jews in Palestine were literate. Once again, these would be the people who could read and maybe write their names and copy words. Far fewer could compose sentences, paragraphs, chapters, and books. And once again, these would have been the urban elites.
Source: Ehrman, Bart D. (2012-03-20). Did Jesus Exist?: The Historical Argument for Jesus of Nazareth (Kindle Locations 702-712). Harper Collins, Inc.. Kindle Edition.