The juvenile works of Mozart have exerted a persistent fascination on scholars. Showing a genius at work who had not yet achieved full grasp of the compositional strategies, they allowed to reveal the tricks and techniques Mozart would later hide and obscure so masterly. The piano concertos K. 37, 39, 40 and 41, his first attempts in this field, have been neglected in this respect, once they had been unmasked as arrangements of keyboard sonatas by other composers. While they fail to qualify as original works, they offer none the less a rich potential of clues about the formation of Mozart's genius under Leopold's supervision. Based on a palaeographical analysis of the autograph scores (now at the SPK Berlin), written in the hands of Leopold and Wolfgang, the article reconstructs the creative process and reveals how Leopold consciously used them as compositional exercises to teach his son a lesson or two in the art of writing keyboard concertos. A comparison with contemporary piano concertos testifies just how innovative even these pre-mature works were (especially with regard to their symphonic scope). They form the prototypes of the Classical concerto, a genre that was just about to emerge at the time and to which already the 11-year old prodigy should make a decisive contributions.