Forty-three percent of 25-34 year-olds have attained secondary education (compared to the OECD average of 82%) and 19% have attained tertiary education (compared to the OECD average of 39%). Turkey has made significant improvement in PISA assessments in mathematics (from 2003-09) and science (from 2006-09), but remains one of the lowest performers among OECD countries in reading, mathematics and science, and the proportion of 15-year-olds who underperformed on the PISA 2009 reading assessment is above the OECD average (Figure 3). The impact of students' socio-economic status on performance and the difference in academic performance between boys and girls are both higher than the OECD average (see Annex B). About 12% of 3-4 year-olds and 67% of 5-year-olds (the typical starting age) are enrolled in pre-primary education. In Turkey, the majority of women with at least one child between 3 and 5 years old do not participate in the labour market (21.4% are employed compared to the OECD average of 64.3%, 2009). To ensure higher upper secondary completion rates, Turkey has increased compulsory schooling from 8 to 12 years, with a starting age of 5.5 years.