Alternative theory to CUP which arg

Alternative theory to CUP which argues that proficiency in English is separate from proficiency in a primary language, and that content and skills in a primary language to not transfer to English language learning (Díaz-Rico & Weed).

The divisional characteristics Separate Underlying Proficiency theory support English-only instruction as the most effective way to learn the language since L2 proficiency is separate from L1 proficiency.