Read the excerpt and answer the question: "Research on bilingual education consistently demonstrates that students who develop strong literacy skills in their first language acquire a second language more efficiently, a phenomenon linguists refer to as cross-linguistic transfer. Contrary to popular assumptions, maintaining and strengthening the mother tongue does not hinder foreign language acquisition; rather, it provides cognitive scaffolding upon which new linguistic knowledge is systematically built. Policies that disregard first-language literacy in favor of exclusive second-language immersion may therefore undermine the bilingual development they seek to promote." The passage's central argument is that first-language literacy: