A straightforward way of keeping children in school is increasing the duration of compulsory education. Evidence of the impact of this type of policy in Western countries is abundant. However, its effectiveness has been rarely tested in low-income countries. Using panel data of low-income and lower-middle-income countries covering the period 1996-2017, this paper analyzes the impact of lengthening the duration of compulsory education on the progression of children from primary to secondary education. The empirical results show that in those countries where this policy is implemented, there is a significant increase in the share of children progressing from primary to secondary education but only in those countries where after the reform the duration of compulsory education becomes longer than the duration of primary education.