This study takes positions on theory, research, and practice in addressing linguistic interdependence among Spanish-English bilingual children in grades 2 - 5. We argue that cross-language associations are likely to vary in part as a function of the construct under study (e.g. syntax vs. lexicon), and as a function of how those constructs get operationalized, or measured.
We looked at how two Spanish language components (syntax and vocabulary knowledge) predict 5th grade English language (vocabulary, syntax, semantics, morphology) and reading. We also examined whether Spanish language predicted 2nd through 5th development in these constructs. Spanish syntax was predictive of all English outcomes in 5th grade, while Spanish vocabulary was not predictive. Spanish syntax was also associated with growth in English semantics. The point being that it does seem to matter what constructs are used and how they are operationalized from a theoretical and methodological perspective. Instructionally, these relationships are not uni-directional, and the fact that Spanish syntax predicts English has instructional implications for thinking about cross-lingustic comparisons to develop general syntactic knowledge which is an accepted component of most models of reading comprehension.
After 12 years, I am not sure if I'll be doing this kind of work in the future, so here is the .pdf if you are interested.