Twenty-first century learning revolves around a pedagogical discourse based on simplistic dichotomies, favoring a student-centered approach. This direction claims that such a learning model will lead to in-depth learning in education. This paper refutes this claim and argues that curricula based on twenty-first century learning promotes a social and context-dependent form of knowledge. To examine the problem of 21st century learning, and to develop an alternative, this paper introduces Bernstein’s pedagogical modalities, which are investigated using the terms “semantic gravity” and “semantic density.” These concepts are used to analyze teachers’ pedagogical practices in three different subjects, considering the further effects of these practices on learning and knowledge-building, as expressed in submitted student papers. The analysis suggests that practices that create long semantic waves, where knowledge is transformed between decontextualized meanings and contextualized meanings, are a condition for in-depth learning and cumulative knowledge-building. The paper argues that this form of knowledge-building is a result of a radical visible pedagogy, which includes practices that are based on different forms of knowledge, making visible how these forms of knowledge can be connected and transformed in education.