Drawing onobservations in texts from the national test in Swedish, the report discusses tworelated questions: 1) whether students develop their writing abilities betweengrades 5 and 9, two measuring points in the system of national tests in Swedish,and 2) how this development might be measured. In the study, two samples ofschool texts – from grades 5 and 9 respectively – were compared in terms of textlength, sentence length and genre match at a macro level. A more detailedanalysis of lexical concentration and text structure was performed on a narrowersample of twenty texts from each school grade. The comparison showed that theolder pupils write longer texts, with longer sentences and a more varied textstructure. The younger children, however, produce texts with higher lexicalconcentration – which might be construed as a higher degree of textual content –and they follow the given genre instructions more closely.