Heritage language speakers constitute a unique cultural and linguistic resource in the United States while also presenting particular challenges for language educators and language programs. This paper examines the potential of systemic functional linguistics (SFL) in a curriculum for Spanish second language learners/heritage speakers, with particular emphasis on the meaning-making of language in the construal of discourse. Following SFL pedagogy, descriptive language teaching refers to ways of treating language in functional terms; productive language teaching involves students in using the resource of their language in powerful ways in light of the demands of particular social contexts. Many heritage speakers have developed their heritage language (Spanish) in the family context but want to be able to use it in the professional areas. SFL with its explicit focus on language allows for the development of advanced literacy in a heritage language in the educational context. Accordingly, the paper discusses explicit instruction of genre/register theory as a way of promoting students' awareness of discourse-semantics and lexicogrammatical features of academic language in courses for heritage speakers. Students' success in developing academic registers in Spanish is evident in their use of lexicogrammatical features (such as grammatical metaphor) that index academic writing. (Contains 4 figures and 6 tables.)