The source of information is a questionnaire filled out by the school in the context of the SNED. Sources of information include regular education statistics at the school level and a SNED questionnaire. The main source of information is a SNED questionnaire. For example, in the Metropolitan Region of Santiago, for a total of 11 groups, the distribution was as follows: 3 groups for urban primary schools, 3 groups for rural primary schools, 3 groups for urban secondary schools, 1 group for rural secondary schools, and 1 group for special education.