Terminology surrounding language programs is often confusing and varies by State and by organization. We stick with the definitions given by the Center for Applied Linguistics (CAL).
Types of Program relate to the population of the school. For example, a dual language program in a school where there is no significant percentage of the population which speaks the partner language is referred to as a “language immersion program” or a “one-way language program”.
Models relate to the amount of time the partner language is taught, the subjects that are taught in the partner language, and/or every how often children switch between native and partner language. For example, a school can have students immersed in the partner language 90% of the time (usually specials like PE and art or music are not in the partner language) in Pre-K 3 and 4 and switch to a 50/50 model from Kindergarten onwards where they learn in the partner language only 50% of the time.
We also have a Glossary for you from our friends at CAL.