This paper explores the reading difficulties of children growing in poverty. At the beginning of the 1st school year, 60 children were given tests of phonological sensitivity, phonological memory, rapid naming, letter knowledge, reading and spelling of familiar words, identification of reading actions, vocabulary and non verbal intelligence. At the end of the year two groups were identified: 25 good readers and 24 poor readers and their initial cognitive profiles were retrospectively compared. No statistically significant differences were found in vocabulary knowledge, intelligence or identification of reading actions. There were significant differences in phonological processing and alphabetic knowledge. Additionally, the performance gap between good and poor readers widened during the year. These results were interpreted as indication that the difficulties of children growing in poverty are the consequence of the interaction between cognitive factors and school instruction.