Typing is not formally taught at school in most European countries, despite digital activities being increasingly prevalent in children's curricular requirements. Typing skills presumably emerge from informal practice, modulated by the availability and use of tools at school or at home. The cognitive processes leading to typing skill acquisition in children have not been described in any detail. To characterize the acquisition of typing skills across school years, we collected data from children schooled in grades 4 to 9 using a questionnaire on typing practice and various chronometric tasks. In our cross-sectional sample of 131 children, the time spent typing or handwriting was stable over grades, but the self-reported number of fingers used for typing increased with grade. The chronometric tasks required typing single letters (alphabet), single words (word copying and picture naming), and sentences (copying and composition). Across tasks, typing speed increased and keypress duration variability decreased with grade. Typing performance for single keystrokes and for words was modulated by a combination of psycholinguistic factors and physical constraints, whose influence decreased with grade, pointing to the ongoing - yet incomplete - organization of the typing process. Text composition performance was highly correlated with performance in text copying. These findings are interpreted with reference to previous results in adults and models of typing expertise. Quantifying the evolution of typing performance opens avenues to fully understand the cognitive processes underlying the acquisition of typing skills and the generation of typing behavior.