Dr. Aída Walqui, a leading expert in academic language development, developed a research-based approach that combines rigorous academic content with high levels of linguistic support. Her framework emphasizes that English learners—especially Long-Term English Learners (LTELs)—can thrive when they are challenged intellectually and supported linguistically and socially.

Jim Cummins is widely known for his influential theories and research in the field of second language acquisition, particularly for his work on bilingual education and the development of academic language proficiency in multilingual learners. He is particularly recognized for his distinction between BICS (Basic Interpersonal Communicative Skills) and CALP (Cognitive Academic Language Proficiency), and for his advocacy of additive bilingualism. 

Michael Halliday's language theory, known as Systemic Functional Linguistics (SFL), views language as a social semiotic system. He believed language is not just about structure but about how people use it to make meaning in different social contexts. Halliday identified three metafunctions of language: ideational, interpersonal, and textual, which represent how language constructs our experience, enacts social relationships, and creates coherent text.

Vygotsky's theory, known as the sociocultural theory of cognitive development, emphasizes the crucial role of social interaction and culture in learning. It suggests that learning is a social process where individuals construct knowledge through interactions with others, particularly those more knowledgeable, like teachers or peers. This theory helps teachers by highlighting the importance of creating collaborative learning environments and providing appropriate support to students as they navigate the zone of proximal development (ZPD).