A major handicap for Portugal has been the very low starting point in terms of educational attainment and literacy of its population. A fifth of all 15- to 64-year-olds were illiterate in the mid-1970s and less than 5% had completed upper secondary education. Nevertheless, efforts to ensure access to education for all Portuguese resulted in a rapid expansion of enrolment. The proportion of the population that has attained at least upper secondary education grew from 14% for the generation aged 55-64 in 2009 to 48% for the generation aged 25-34 in the same year. Despite the expansion of the education system, educational attainment remains a challenge. It is the lowest in the OECD area for the working-age population, with 30% of 25- to 64-year-olds having attained at least upper secondary education in 2009 (against an OECD average of 73%). Moreover, the high share of students leaving the education system too early with low skills remains a major problem.