Video coding
As mentioned earlier, within each phase, 20% of the recorded films will be randomly selected and evaluated by two external raters at item-level across the five primary outcomes. Agreement between the two raters and the teachers will be checked, and in case of agreements below 80%, all the films will be checked. The research assistant will be blinded to when the intervention will start for each student. We have operationalized all aspects of the testing, drew up observation criteria, and made a check list that will be followed when observing the videos. The teachers will record answers during the testing, and the researcher and the researcher assistant score the films blinded for each other on the basis of the checklist in order to calculate the interobserver agreement.