In sequential bilingualism, learners receive literacy instruction in their native language until they acquire a "threshold" literacy proficiency. Some researchers use age 3 as the age when a child has basic communicative competence in their first language (Kessler, 1984). Children may go through a process of sequential acquisition if they migrate at a young age to a country where a different language is spoken, or if the child exclusively speaks his or her heritage language at home until he/she is immersed in a school setting where instruction is offered in a different language.