Abstract: Over the past few years, multiple anxiety prevention programs for teenagers have been developed and implemented in schools. However, these programs are seldom systematically evaluated and scaled up for use in all schools. When the programs are evaluated, data collection often involves the use of a logbook completed by facilitators. This method’s specific methodological function in a program evaluation involving multiple data sources has not been systematically analyzed to date. This article uses the example of the HORS-PISTE program to show the logbook’s advantages, limitations, and challenges as a data collection method.