Is teacher certification an effective tool for developing countries?

Teachers are perhaps the most important determinant of education quality. But what makes a teacher effective? Developing countries expend substantial resources on certifying teachers and retaining those who become certified; moreover, policymakers and aid donors prioritize increasing the prevalence of certified teachers. Yet there is little evidence that certification improves student outcomes. In fact, augmenting a school's teaching corps with contract teachers hired outside the civil service and without formal qualifications may be more effective in boosting student performance.