Several current spelling models suggest that children cannot have any knowledge of orthographic form before they have acquired knowledge about orthographic function. We evaluated this proposition by using an orthographic choice task to inspect Finnish schoolchildren's knowledge of two aspects of consonant doublet use: the allowed doublet position (an aspect of orthographic form) and the type of phonemic information they represent (an aspect of orthographic function). The results challenged the view of the existing spelling models, since they showed that already at the beginning of the first school year children possessed formal knowledge of doublet use and knew that word-initial doublets are not allowed. However, these children were ignorant of the function of doublets, i.e. that they stand for long consonants.