English orthography differs from that of other European languages in terms of complexity and regularity. This difference may impact the development of accurate spelling in English, especially when it is learned as a foreign language in school. In this study we wanted to explore spelling development patterns of Spanish speaking children learning English at school. To do so, we analyzed spelling errors from a free narrative task from 136 children in fourth, fifth and sixth grades. We classified errors following a two-level procedure based on the Triple Word Form theory (Phonology, Orthography and Morphology) and the POMAS (Phonological, Orthographic, and Morphological Assessment of Spelling) system. While results showed almost no change in accuracy across grades, there was evidence of more errors related to orthography as compared to phonology and morphology. This points to an incomplete knowledge of English orthography. This study sheds light on the spelling development of foreign language learners, and illustrates the interference that the native language may have when the two orthographies of the speller are linguistically distant. Considering the findings, educational implications to improve foreign language spelling instruction at school are offered.