An OECD assessment found 64% of Icelanders aged 25–64 have earned the equivalent of a high-school degree, which is lower than the OECD average of 73%. Among 25–34 year-olds, only 69% have earned the equivalent of a high-school degree, significantly lower than the OECD average of 80%.[75] Nevertheless, Iceland's education system is considered to be of excellent quality: the Programme for International Student Assessment currently ranks it as the 16th best performing, above the OECD average.[141] Students were particularly proficient in reading and math.