The aim of this work was to build an objective tool for the detection of graphomotor difficulties involving disorders in the writing of children. We outline some characteristics of layouts, describing the automation level of the graphic activity. We have defined exercises, like copying figures or writing sentences under different conditions that allowed us to measure simple aspects of graphomotor skill up to complex ones. A tool was conceived which was able to automatically extract low-level and high-level primitives. Based on such descriptors, we focus on the analysis of the temporal structuring of two particular drawings. In the final part, we present the method we used to select features that can describe the automation level of the graphic activity and we show that, in most cases, these features allow to discriminate children with academic difficulties.