Measuring inequality of learning outcomes in a way that provides meaningful benchmarks for national policy while retaining a focus on those students who are ‘hard to reach’ and ‘hard to teach’ is a challenging but vital task in the light of the global post-2015 education agenda. Drawing on PISA 2012 data and its earlier rounds, this paper explores alternative approaches to measuring educational inequality at the ‘bottom-end’ of educational distribution within the cross-national context. Its main aim is to understand how far behind children are allowed to fall in their academic achievement compared to what is considered a standard performance in their country. Under the framework of relative (measured as achievement gap between the median and 10th percentile) and absolute (measured by the percentage of students achieving at a given benchmark) educational disadvantage it examines cross-country rankings as well as national trajectories with reference to overall academic progress. It is found that on average across OECD countries around 11% of 15- year-olds lacked skills in solving basic reading, mathematical, as well as science, tasks in 2012, but variation across countries was large.
