Research consistently shows that language and literacy development in the student's native language not only facilitates learning English and English literacy, but is foundational to cognitive development and learning (Cummins, 2001; Thomas & Collier, 2002; Coelho, 2001). Emergent bilinguals (Sparrow et al., 2014; Slavin & Cheving, 2013) are students who are in the process of acquiring two or more linguistic codes, becoming bilingual, biliterate, and bicultural. Emergent bilinguals are often defined by their perceived deficits (semilinguals) (Escamilla, 2012). However, research has shown that bilinguals develop a unique interdependent system (Escamilla et al. 2007; Grosjean, 1989; Valdes and Figueroa, 1994) in which languages interconnect to increase linguistic functionality. This linguistic interdependence of language acquisition facilitates a transfer of literacy skills from the primary language (L1) to the second language (L2) (August & Shanahan, 2006; Bialystok, 2007; Miramontes, et al., 1997). The strength of learning through formal instruction in Spanish determines the extent of transfer to English (August, Calderon, & Carlo, 2002; Slavin & Calderon, 2001; Garcia, 2001). For transfer to be maximized, cross-linguistic connections between the two languages must be explicitly taught while students engage in a contrastive analysis of the Spanish and English languages (Cummins, 2007). Continued strong literacy development in Spanish provides the foundation and scaffold for literacy development given that a Common Underlying Proficiency (CUP) exists between the two languages (Cummins, 1991). Consequently, direct and systematic instruction (Genesee et al., 2005) in the appropriate sequence of Spanish skills with early English as a second language-based literacy instruction is critical to student success. As a result of working within two language systems, students' metalinguistic and metacognitive skills are enhanced when they learn about the similarities and differences between languages (Escamilla et. al., 2014). The extent to which English and Spanish are used is reliant on the type of bilingual program model being used (see Texas Education Code, §29.066).
