Software for supporting pupils in learning reading and writing skills is very often less productive than expected. A main reason for this is that pupils who are not able to read and write do not succeed in using complex software environments which are furthermore very often designed like old-fashioned tutoring systems. Taking the results from the EU founded project NIMIS as a starting point for a Ph.D. thesis [1], in this paper an approach to analyse writing products of German first graders who use a phonetic based method to learn reading and writing skills will be presented. From these analysis results a learner model is build which maps the knowledge level a child has reached in the process of phonetic writing.