* Varying definitions of "graduating": Different countries have different educational systems and standards for graduation. Some might allow students to graduate with significant learning deficiencies, while others have stricter requirements.
* Data collection challenges: Tracking literacy rates among graduates specifically is difficult. Many education systems focus on overall graduation rates, not detailed breakdowns of skills like reading proficiency.
* Iliteracy vs. functional illiteracy: Someone might technically graduate but struggle with reading at a functional level. Distinguishing between complete illiteracy and functional illiteracy in official statistics is complex.
While exact numbers are unavailable, it's safe to say that in some parts of the world, a significant number of students graduate high school with inadequate reading skills. The problem is more pronounced in disadvantaged communities and countries with under-resourced education systems. Organizations like UNESCO and various national education ministries collect data on literacy rates, but rarely focus on the specific subset of high school graduates who are illiterate.