This study examined the issue of transfer for low-intermediate ESL students enrolled in an academic English development course at the community college level, Late immigrant students (adult immigrants) had higher LI academic language proficiency and generally made better progress in L2 academic language development as a result of instruction than did the early immigrant group (those who immigrated at a younger age). The findings support Cummins' Model of Common Underlying Proficiency (CUP) and the Interdependence Hypothesis between L1 and L2, complement previous studies on literacy development in first and second languages, and provide both quantitative and qualitative evidence on positive transfer of prior linguistic and cognitive skills from L1 to L2.