according to school principals who participated in pisa the average student across oecd countries attends a school where of teachers have been fully certified but this proportion ranges widely from in macao china to around in colombia findings show that the proportion of teachers who have been certified to teach is positively associated with student performance in only a few selected countries both before and after accounting for the socioeconomic profile of students and schools figure this overall weak impact is not surprising given the different standards used in different countries to certify teachers and the fact that most countries have a high percentage of certified teachers