Tabors, P.O., Paez, M. M., Lopez, L.M. (2003). Dual Language Abilities of Bilingual Four-Year Olds: Initial Findings from the Early Childhood Study of langauge and Literacy Development of Spanish-speaking Children. NABE Journal of Research and Practice, Winter 2003, pp 70-91.
This article looked at the early literacy skills in Spanish and English for a sample of 344 bilingual children in MA, Maryland, and Puerto Rico and compared then to a control group of children. The results suggest that bilingual children are not different across groups on tasks of phonological awareness. Differences were found for the subgroup of students from MA and Maryland who scored significantly lower in oral language subtests of the Woodcock Language Proficiency battery in both languages when compared to the control group and the Puerto Rico subgroup. On average the children from Puerto Rico scored better that the MA and Maryland subgroup in Spanish oral language skills.
Read more by accessing the journal article. A follow up on this study is soon to come out as well!