In New Zealand, bilingual education and immersion education have tended to be regarded as quite distinct from one another. However, the international research literature consistently identifies immersion education as one form of bilingual education (May & Hill, 2008).
Educational approaches to bilingual education also vary widely in relation to how effectively they foster or promote bilingualism, biliteracy, and academic success for bilingual learners.
Janet Holmes’ early definition of bilingual education in New Zealand can still be applied today:
A bilingual education programme is one intended to promote bilingualism either by the predominant use of a minority group language [that would not otherwise be maintained] or by the use of two languages as mediums of instruction in school. (Holmes, 1984:1)
Put simply, bilingual education involves instruction in two languages. For a programme to be deemed to be bilingual, the key is that both languages must be used as a medium of instruction and to deliver curriculum content.
On this basis, immersion models that teach predominantly through a minority language are also clearly bilingual programmes. Curricular instruction in the majority language (English, in both cases) almost always occurs at some point prior to the end of the programme, even in those programmes with very high levels of immersion in the minority language. There are specific issues with respect to ensuring that academic language proficiency in both languages occurs – that is, the successful achievement of biliteracy.
An additional key point addressed by many commentators in defining bilingual education relates to the goals and outcomes of any given programme. In short, does the programme in question aim to achieve, foster and/or maintain longer-term bilingualism and biliteracy (additive bilingualism), or does it aim eventually to shift learners from bilingualism to monolingualism in the dominant language (subtractive bilingualism)?
Additive bilingual programmes are regarded as strong forms of bilingual education. Additive bilingual education approaches include those that teach in learners’ first language, if this language is different from the majority language, in order to promote eventual bilingualism and biliteracy. This approach is based on the developmental interdependence principle, where acquiring literacy in one’s first language is seen to provide the strongest basis for successfully transferring these literacy skills to a second language such as English (May, 2008).
In New Zealand, such an approach is most congruent with Pacific bilingual education, since many Pacific families still speak a Pacific language in the home and/or in community contexts. By implication, additive bilingual education would also include programmes that aim to foster bilingualism but which have a mix of both first language and second language speakers, similar to the Dual Immersion bilingual education programme in the United States of America, which predominantly focus on Spanish and English. This model could potentially apply to Pacific language education programmes in New Zealand.
In a subtractive bilingual context, the bilingual learners’ first language has low status and is not valued by the school or the wider community, nor is bilingualism in this particular combination of languages seen as desirable or useful. Consequently, the educational aim is to ‘shift’ the bilingual learner to the second language as quickly as possible. The result is actually a significantly lower likelihood of the learner becoming bilingual and, in most cases, the eventual loss of the learner’s first language.
A subtractive bilingual context also exhibits the lowest rates of educational success in achieving literacy in the second language for bilingual learners, not least because of the erosion of learners’ cultural identity and self-esteem and the difficulties inherent in acquiring academic language proficiency in a second language (May, 2001).
There is significant research demonstrating the advantages of additive bilingual education on learner achievement in mainstream English-medium programmes (Pacific Policy Research Center, 2010). There is a strong case in the research literature for bilingual education as a means of lifting Pacific attainment, rather than the current focus on English language attainment in mainstream English-medium programmes (Hill, 2017).
According to Freeman (1998), models are defined in terms of ‘their language-planning goals and ideological orientations toward linguistic and cultural diversity in society’. They are broad categories that help us to understand on a very general level what bilingual education means. It could also help schools to be clear about the purpose of providing bilingual education, in relation to the aims of bilingualism and biliteracy, and their learning community’s desires.
May (2008) synthesized the models into meaningful categories that highlight broad agreements among researchers. Table 1 below is a general summary of the nature of bilingual education models.
Transitional bilingual education typically begins in early learning year, by using the learners’ first language (L1) as the media of instruction but the aim is leave the learners’ L1 capabilities behind and develop only their second language (L2) linguistic and academic proficiencies. Transitional bilingual education programmes aim to stop teaching in the learners’ L1 after 1-2 years. The aim of a transitional bilingual programme is eventual monolingual teaching and learning, usually in the dominant language. It is clearly not bilingualism or biliteracy.
Maintenance bilingual education programmes do not involve development or extension of the minority language. They are limited to maintenance of the minority language which, when compared to transitional programmes is considered additive and fairly strong. The learner’s L1 and, by extension their sense of culture and identity is affirmed by the programme. Education in the L2 may begin at an early phase, perhaps as much as 50% of the time (May, 2008), but the emphasis of the early years is clearly on L1 proficiency and academic achievement using the L1. A maintenance bilingual programme aims to form a solid academic base for the learner in their L1 that “in turn facilitates the acquisition of literacy in an L2, on the basis of the developmental interdependence principle” (Cummins, 1979; Cummins, 2000).
Enrichment bilingual education focuses on teaching learners academic proficiency through the medium of a second language, whereupon literacy in the second language can be attained. The goal of enrichment programmes, just like maintenance programmes, is bilingualism and biliteracy for individual learners and also maintenance of the minority language in the community. Enrichment programmes differ from maintenance programmes in that they specifically seek to extend the influence of the minority language in an integrated national society. The goals are more than linguistic. Enrichment programmes aim for cultural pluralism and autonomy of cultural groups.
Heritage is the fourth general model type that fits roughly between, and overlaps, both maintenance and enrichment. Its distinguishing feature is the programme aim, which is generally a recovery of lost or endangered languages.
Bilingual education models
 Pacific Policy Research Center, 2010.