It has been shown that when students are placed in a classroom where the students are fully exposed to English without any support or aid, the learning of the students often decreases. This is because when they are submerged with their limited English proficiency in a completely English-only classroom, they are so often frustrated with trying to figure out the meanings of words that they struggle to make sense of what they are hearing and learning. Teachers in submersion classrooms such as these, are also not certified to teach ELLs and have not been taught how to help them develop their English. (Wright, 2015) They basically leave English Language Learners to either sink or learn to swim. If students are introduced to English over time, as through the Transitional Bilingual Program, the students have no chance of falling academically behind their English speaking peers because the instruction is taught in their home language for a certain percentage of time as they acquire English Language proficiency. This time of native language instruction decreases as the students move up in grade level and English proficiency. (Wright, 2015) This method encourages student academic success as it helps students gradually acquire proficiency in English, and the student's acquisition also has a higher chance of developing quickly when the students do not feel overwhelmed or stressed, which are the feelings that the submersion method evokes.
References:
Wright, W. (2015.) Instructional Programs for English Language Learners. In Foundations for Teaching English Language Learners: Research, Theory, Policy, and Practice ( Second Ed., pp. 97-111) Phhiladelphia, Pennsalavinia: Carlson Inc.
Sink or swim. (2011, February 13). Retrieved September 28, 2015, from http://www.between-us-bilinguals.com/sink-or-swim.html