12th Century literacy
The majority of the 12th century populace was illiterate. This was not something imposed by the upper classes upon the lower, but instead simple a consequence of literacy being of little use to farmers and suchlike.
For those who were well to do, but not noble, occasionally schools would be run in town by clerics for a small fee. These would teach only the basics of learning. Boys who learnt well here could go into the clergy and follow a variety of lifestyles from itinerant preacher, monk, teacher or pursue a career in academia if their skill was sufficient to attract a patron.
Nobles (or presumably anyone else with such a large budget) could employ a tutor to teach individual children or small groups of children. Noble girls and boys were taught alike, often the noble girls ending up with a better level of literacy than the boys who left earlier to become knights.