Completion rates are usually lower for students with a disadvantaged background (e.g. lower educational status of parents, first-generation immigrants) (OECD, 2017(h) (OECD, 2016(6]). In most countries, repeaters tend to be concentrated in the last two years before graduation, while in some others the distribution over different grades is more even. In a smaller number of countries, repeating grades is restricted by law and school regulations, and the concept of repeating does not even exist, especially at lower educational levels.