There is a lot of advice to parents of ESL children elsewhere on these pages. However, the most important message can be summarized in one sentence:
ESL students in international schools learn English more quickly and effectively if they maintain and develop their proficiency in the mother tongue.
How does the mother tongue help the learning of English? Research* has shown that many skills acquired in the first language can be transferred to the second language. So, for example, if your child has developed good reading skills in Korean, she is likely to be able to apply these skills when reading English. (One useful reading skill is the ability to guess the meaning of unfamiliar words from context. Another one is the ability to decide which new words in a text are important to look up in the dictionary and which words can safely be ignored.) For this reason it helps if you can encourage your child to read good fiction and non-fiction in her own language. Similarly, the skills of being able to plan out a piece of writing or develop an argument in a persuasive essay can be applied in the second language once they have been learned in the first.
What are the other reasons for maintaining and developing mother tongue proficiency? Firstly, many children in international schools plan to return to their home country at some point to continue their education there. This is a strong reason to make sure they do not have gaps in mother tongue language or cognitive development. And secondly, ESL students who turn against or otherwise neglect their mother tongue can often suffer from problems of identity loss or alienation from their parents, and from their grandparents or other family members in their home country.
How can ESL students best develop their mother tongue proficiency? For some students, developing mother tongue proficiency is easier because they have lessons each week in their native language. For students who are not in this fortunate position, there is still much that can be done to maintain the mother tongue. For example, parents can make sure that they have good reference books or textbooks at home - in the native language. Students should be encouraged to read good literature and to discuss school work. Some of the long summer vacation could be devoted to mother-tongue learning and reading.
The advice on this page is so important that it is repeated in the yellow text below. [Click to see the advice in graphic form.]
Your children will learn English much more effectively if they continue to develop their first language at the same time.
* "In early stages it [reading in the first language] can profoundly accelerate the development of reading ability in the second language."
This is true because:
Krashen, S. (2004) The Power of Reading: Insights from the Research. Heinemann. Portsmouth.