Dyslexia is a specific disorder of language. Researches led on dyslexia origin have conducted to multiple hypotheses and various rehabilitation treatments. In this context, practitioners can be interested in using an automatic tool to help in diagnosing dyslexia. This tool should evaluate children's own deficit and advise adapted rehabilitation. This paper presents the conception of a preliminary test containing the most representative dyslexia evaluation tasks from literature and the first results concerning the discriminatory validity of this preliminary test in French school age children (8-10 years). Moreover a selection of significant tasks to optimize the detection of dyslexia is proposed. These tasks will build up the first step of the automatic tool.