Starting point are all primary schools in Morazan, excluding the 50 smallest schools with only one or two teachers covering grades 3--6. The NGO sent out invitations to all eligible teachers in these schools, who were asked to register via telephone, internet or filling out a registration form.
Based on these registrations the applicants were invited to an information meeting in March 2019, where an unannounced baseline math assessment was conducted. Some of the applicants took exactly the same assessment during a representative survey in September 2018 (about 6 months before), and therefore only completed the registration and received additional information about the program.
Based on the baseline assessments, the worst performing applicant of every school was selected; applicants were informed that participation in the March-meeting did not guarantee admission to the program, but the pre-selection criteria were not communicated to them. Following this procedure 175 teachers from 175 different schools across Morazan remained in the sample.
Stratifying on baseline scores and teacher gender, the 175 teachers were randomly assigned to the either the control or treatment group. This gives 87 teachers that participate in the program and 88 teachers constituting the control group.