Processing fluency-the experienced ease with which a mental operation is performed-has attracted little attention in educational psychology, despite its relevance. The present article reviews and integrates empirical evidence on processing fluency that is relevant to school education. Fluency is important, for instance, in learning, self-assessment of knowledge, testing, grading, teacher-student communication, social interaction in the multicultural classroom, and emergence of interest. After a brief overview of basic fluency research we review effects of processing fluency in three broad areas, namely metacognition in learning, belief formation, and affect. Within each area, we provide evidence-based implications for education. Along the way, we offer fluency-based insights into phenomena that were long known but not yet sufficiently explained (e.g., the effect of handwriting on grading). Bringing fluency (back) to education may contribute to research and school practice alike. FLUENCY IN EDUCATION 3 In the last decades, school education systems in many countries have been inspired by central tenets of cognitive psychology. The symbolic mental processes examined by cognitive psychologists are often implicit to the way teaching and learning at school is conceptualized. An important branch of cognitive research deals with metacognition, that is, cognition about cognition, such as knowledge about cognitive processes, or strategies to monitor or control cognitive performance (Flavell, 1979). Metacognition further encompasses subjective experiences or feelings that arise when a mental operation is performed. Such metacognitive feelings include, for instance, feelings of knowing, feelings of familiarity, feelings of rightness, or feelings of coherence, that all depend on processing fluency (or just fluency; e.g.,