"Bilingual Education" is often used to refer to all programs designed to assist students who are not fluent in English when they arrive in US schools, but it is not one cohesive program.

There is significant argument over several points, including:
Whether students should be taught in their native language;
Whether students should be taught to read, write, and otherwise be literate in their native language;
How long students should receive assistance in learning to use English; and
How students will best learn English.

There are other questions that come into the decision of how these students will be taught, from the practical questions such as "How many students do we need to be able to hire a separate teacher?" to more philosophical ones, such as "What is our duty to these students?"

Often these decisions are based on the history of the region involved, whether there have been heated court cases that have determined what must legally be done, or powerful groups promoting one method or another.

In any case, it is often difficult to determine exactly what is being done in different schools, as each school or district may interpret what a specific policy requires that they do or don't do. This makes research into the comparative effectiveness of programs difficult, as do the sometimes widely different goals of different programs.

As often happens in the discussion of Bilingual Education, we offer here only general discussion of commonalities between programs going by each of the names we discuss, and any given program may be different from our description in many ways.