The history of schools in recent times has extended its field of study owing to the use of new sources. Traditional sources have been joined by oral testimonies, images, objects, ego-documents, ethnographic descriptions, and all sorts of sources that enable us to look into the lesser explored areas of schools in the past. These new testimonies are what make it possible to find out about what some authors have called the Black Box of Schooling, what happened in classrooms on a daily basis. In this article, with the aim of opening this black box and learning more about state schools in post-war Spain, we focus on the analysis, through the historical method, of one of these new sources: teaching practice reports of Primary School student teachers. The sample is made up of an unpublished collection of nearly a hundred teaching practice reports from the Primary Teacher training college in Balearic Islands, drawn up between 1939 and 1948, in order to learn about school practices in these schools. This analysis enables us to evidence that, beyond the stereotyped view that we have of Francoist schools and of their school culture, determined by their ideological impositions and legal regulations, there exist aspects that we can only learn about if we take a look at the everyday workings of the classroom. In this sense, this article provides historical knowledge regarding Francoist schools and the configuration of their school culture. This article shows, as also happens today, the fact that some continuities have historically resisted the political will to introduce changes. It shows the distance between what has been prescribed by law and what actually happens in schools. This finding suggests getting away from historical interpretations that have only been based on administrative sources, to add to the History of the School all those testimonies that bring us to the realities of the classroom. These observations should be take into account before considering any reform of the school system