The benefits of learning two languages

• Educational: Achieve L2 without consequences on L1.
• Cognitive: Advanced levels of proficiency and linguistic advantages.
• Social-cultural: Expansion of their world view.
• Economic: Employment opportunities.

Source: Cloud, N., Genesee, F., & Hamayan, E. (2000). The Benefits of Knowing Two Languages. In Dual Language Instruction: A Handbook for Enriched Education (pp. 2-4). Boston: MA: Heinle & Heinle.

Developmental or Maintenance Bilingual Education

Purpose: To develop bilingualism and biliteracy proficiency and to achieve academically at grade level.

English language learners (ELLs) maintain and develop their native languages as they acquire English. 
Students initially receive most instruction in their native language as English is added in increasing amounts each year. By fourth or fifth grade, students receive instruction equally in both languages.

This additive program exists where there are sufficiently large numbers of students of one language background to make it possible to hire bilingual teachers and where there is interest and support in the community for having a bilingually educated population. 
  
Criticism: The main obstacles to implement this program in the Chilean education system are the necessity of having: qualified bilingual teachers and active support from ELLs and their family. 

Source:  
"IRIS | Developmental Bilingual Education". Iris.peabody.vanderbilt.edu. N.p., 2017. Web. 8 Apr. 2017.
 Soltero, S. W. (2004). Program Models For Second Language Learners. En S. W. Soltero, Dual Language: Teaching and Learning in two Languages (pág. 4-5). Pearson.

Two Way Immersion

In the United States, two-way immersion (TWI) is an educational approach that integrates native English speakers and native speakers of another language (usually Spanish) for content and literacy instruction in both languages

Origin: The initiation of dual immersion programs in the United States is characterized by the coalescence of local politicians and community members. Coral Way Elementary, a K-8 school in Dade County, Florida, is cited as the first two-way bilingual school, beginning in 1963. The program was started by Cuban citizens who were seeking refuge in Florida from the Castro regime and believed that their children would eventually return to Cuban schools

Goals:

Students will develop high levels of proficiency in their first language:  

This means that native English speakers will develop high levels of speaking, listening,

reading, and writing ability in English, and their performance in these domains will

not be compromised by their involvement in a bilingual program. Likewise, the

language. minority students will develop high levels of speaking, listening, reading,

and writing ability in their native language (e.g., Spanish) and will not be asked to

forgot development in their native language as their second language proficiency

improves.

All students will develop high levels of proficiency in a second language: 

For the native English speakers, this means that they will have the opportunity to

develop high levels of oral and written proficiency in a second language, such as

Spanish, French, or Korean. For the language minority students, this means that

they will develop high levels of oral and written proficiency in English, and that their

English language and literacy development will not be diminished because they are

also continuing to receive instruction in their native language. For this reason, TWI

programs are considered additive bilingual programs for both groups of students;

they afford all students the opportunity to maintain and develop oral and written

skills in their first language while simultaneously acquiring oral and written skills in a

second language.

Academic performance for both groups of students will be at or above grade

level: 

The same academic standards and curricula that are in place for other

students in a school district will be maintained for students in TWI programs as

well. Academic requirements are not diluted for TWI students, and the same levels

of academic performance are expected for both TWI students and students

enrolled in other programs throughout the district.

All students will demonstrate positive cross-cultural attitudes and behaviors:

Because TWI programs provide instruction in an environment that is integrated

linguistically, racially and ethnically, and socio-economically, they allow students to

learn first hand about cultures that are different from their own.

• Students learn through social interaction

• It attempts to all students be bilingual

• Classes are composed of students who are native English speakers and students who are from other language and cultural background

• It develops positive cross-cultural attitudes

• This program should provide a minimum of 4 to 6 years of bilingual instruction

• It is imperative that teachers use sheltered instruction strategies to  make the content comprehensible to all students 

• Instructional time is divided between English and a second language 50/50 and 90/10

Grade level	90/10 model	50/50 model
K	90	50
1	90	50
2	80	50
3	80	50
4	50	50
5	50	50
6	50	50

Criticism:  In the Chilean context the implementation of a TWI program seems to be extremely challenging, due to the current conditions among the public schools, English is not generally part of the curriculum in earlier grades and when it is included it does not follow the social cultural principles of integration due to the fact that students come from the same origins and they are already integrated.    

Source:

Howard, Elizabeth R. y Donna Christian. Two-Way Immersion 101: Designing and Implementing a Two-Way Immersion Education Program at the Elementary Level. Santa Cruz: Educational Practice Report, 2002. Center for Research on Education, Diversity & Excellence.

"Dual Language". En.wikipedia.org. N.p., 2017. Web. 7 Apr. 2017.