An ELT Glossary : Language Immersion Programmes / Bilingual Education

Children participating in a language immersion programme receive anything from 50-100% of their school education in a language which is not their L1. For example English speaking children attending a French-medium school in Canada.  If both languages are used, the programme may also be referred to as bilingual education. 

Further reading 

What Parents Want to Know About Foreign Language Immersion Programs  ~  Fortune,T.W. Tedick, D.J. D