This study aims to understand if children’s spelling errors vary according to their orthographicperformances and their grade level. It also aims to understand the way in which children’s awareness oforthography rules relates to their performance. The participants were forty-three children (24 boys and 19girls) attending the third grade and, the following year, the fourth grade in a Lisbon public school. Theywere given a spelling task in third grade and again in fourth grade and their spelling errors were compared.In fourth grade, the types of error of good and poor spellers were compared. Interviews were conductedto determine if the level of awareness of orthographic rules differed according to the children’sorthographic performance. The results show that the number of errors decreased from the third to thefourth grade and that there are differences in the types of error made by participants with higher andlower orthographic performances. There were no statistically significant differences between these twogroups concerning their awareness of orthographic rules.