This happens when an official language is used more often and children stop learning the local language of their parents.

VOA: special.2009.12.02

(Speech) Iran's official Arabic-language al Alam TV is reporting (No Transcripts) The Iranian Student News Agency reported earlier the head of the parliament's national security committee, Alaedin Borujurdi, would put the U.N.draft nuclear deal between Tehran and the West to a vote of his committee after discussing its pros and cons.

VOA: standard.2009.10.28