WCAG 2.0 and Reading Level
It is always a good idea to make content as readable and understandable as is suitable for the audience. For complex content (defined as that which requires a reading ability more advanced than the lower secondary education level), WCAG 2.0 Success Criterion 3.1.5 (Level AAA) requires that a more simplified and readable version of the content be provided. Much content cannot be made perfectly understandable at these levels (consider a college-level chemistry class, for example), thus it’s a Level AAA success criterion. Regardless of the limitations for some content, for a page to be optimally accessible, it should be written so as to be easily readable and understandable to the target audience.
