Raising a Bilingual Child in Japan: 7 Research-Backed Tips for Families

By Naveen Bukhari, Vice Principal

Your family talks, laughs and plans in Japanese. And you would love your child to grow up comfortable in both languages: making friends, reading, thinking and one day working in English as naturally as in Japanese.

Is that realistic in Japan? The research gives a hopeful answer, and parents play a bigger part than many expect. Here it is, turned into seven practical tips.

First, the good news: two languages don't confuse children

One of the most common worries is that two languages will overload a child or slow down their speech. Researchers Krista Byers-Heinlein and Casey Lew-Williams reviewed the evidence on exactly these questions. Their conclusion is that children are born ready to learn the language or languages around them without confusion or delay. Bilingual children are not more likely than monolingual children to have language difficulties or disorders.

Why, then, do some bilingual children seem "behind"? A study by Erika Hoff and colleagues at Florida Atlantic University explains. Bilingual toddlers knew fewer words than monolingual toddlers when each language was tested on its own, but their total vocabulary across both languages was comparable. Your child is not learning less. They are spreading what they learn across two languages.

Tip 1: Think in hours, not in rules

In the same study, Hoff's team found that children's vocabulary and grammar in each language were related to how much of their input came in that language. Put simply, a language grows in proportion to how much a child hears and uses it.

Byers-Heinlein and Lew-Williams give a striking example. A young child awake about 84 hours a week who hears a language for one afternoon (about 5 hours) is getting only about 6% of their waking week in that language. On its own, that is unlikely to be enough to learn it.

Try this: For one ordinary week, roughly note how many hours your child actually hears and uses English. Researchers recommend this honest check: what your child really hears, not what you hope they hear.

Tip 2: Your Japanese matters, and supporting English doesn't require fluency

Many families have heard of "one parent, one language." It can work well, but it is not magic. In a survey of 1,899 bilingual families, linguist Annick De Houwer found that the one-parent-one-language approach was neither necessary nor sufficient for children to speak both languages.

The researchers' advice is to use whatever approach gives your child plenty of good-quality input in each language, taking into account the languages each family member knows and prefers. You are your child's first and most important language role model in Japanese, so keep talking together in rich, warm, detailed Japanese. Plenty of English conversation can come from school, activities and friends. At home, curiosity, encouragement and routines matter more than perfect English: ask "What did you learn in English today?", or learn a new word together. Learning alongside your child is a strength.

Tip 3: A strong first language is a foundation, not a competitor

It can feel as if every hour of Japanese is an hour "lost" from English. The research suggests the opposite. Jim Cummins of the University of Toronto proposed the "developmental interdependence" hypothesis: how well a child develops a second language partly depends on how well developed their first language is when intensive exposure to the second language begins.

Concepts learned in one language, such as what a fraction is, how a story is built or how to argue a point, do not need to be learned again from scratch in the other.

Try this: Keep reading Japanese books together, talk about the news, ask "why do you think that happened?" in Japanese. You are building the thinking that English will later sit on.

Tip 4: Real people beat screens

Byers-Heinlein and Lew-Williams note that high-quality language input involves social interaction, and that infants do not readily learn language from television. Talking with several different speakers has been linked to stronger vocabulary in bilingual toddlers.

As children grow, friends matter more and more. The researchers point out that playing with other children in a language is an important motivator, especially when that language is not widely spoken in the community, which is exactly the situation with English in Japan.

Try this: Treat English videos as a bonus, not the plan. Watch together and chat about them, and look for chances to play with other children in English.

Tip 5: Don't panic when your child mixes languages

"Can I have the ringo?" Mixing words from two languages in one sentence is called code-mixing. It is a normal part of bilingual development and often follows grammar-like rules. Research on parents' own mixing is still limited, so there is no need to police every sentence. Gently model the word in the other language and keep the conversation going.

Tip 6: Expect "playground English" before "classroom English"

This is the tip that saves parents the most worry. Cummins distinguishes between conversational fluency and academic language: the English needed to explain a science experiment, write a persuasive paragraph or read a textbook. In his reanalysis of data from Toronto schools, immigrant students usually reached conversational fluency in about two years, but needed five to seven years, on average, to approach grade norms in academic English.

Those students lived in an English-speaking country. In Japan, where children hear far less English outside school, patience matters even more.

Try this: Celebrate the first chatty months, then ask your child's school how it builds academic English across subjects, not just conversation.

Tip 7: Earlier is easier, but it's never too late

Researchers still debate whether there is a "critical period" for language. But Byers-Heinlein and Lew-Williams say the evidence converges on a simple point: earlier is better, with a gradual decline in language-learning ability with age rather than a sudden cut-off. They also note that immersion programmes, where the second language is used to teach other subjects rather than only being taught as a subject, often help children become functionally bilingual.

For context, Japan's national curriculum (introduced in 2020) gives English 70 lesson periods across Grades 3 and 4 and 140 across Grades 5 and 6. That is 210 periods of 45 minutes over four years, according to the Ministry of Education's curriculum guide. This is a valuable foundation, but for families aiming for full bilingualism it is usually only part of the picture.

How we do this at YES

At YES International School in Yokohama, these ideas shape daily school life.

• English as the language of learning. Most of our students come from Japanese-speaking families, with a wide range of English levels. Our focus is on moving children step by step towards learning in English only, so English becomes the language they think and learn in, not just a lesson on the timetable.

• A Cambridge education. YES International School is a Cambridge International School, approved for Cambridge Primary and Cambridge Lower Secondary, so academic English grows alongside a recognised international curriculum.

• Deliberately small classes. Small classes mean more chances for every child to talk, ask questions and be heard, which is exactly the kind of real interaction research highlights.

• Bilingual, plus programming. Japanese and programming sit alongside English, guided by our 3 Cs: Consideration, Critical Thinking and Creativity.

Come and see it for yourself

If you are wondering whether a bilingual education is right for your child, the best next step is to see it in action.

• School Orientation: Saturday 17 October 2026, 9:00–11:00, free. Reserve your place.

• Can't make it? We welcome visits any time by arrangement. Applications for April 2027 are open, and we accept transfers throughout the year.

• Contact us: Access & contact · Tel 045-595-9563 (Mon–Fri 9:00–18:00) · info@yesinternationalschool.com

Reserve your place at the School Orientation

You'll find us near Yokohama Station (Nisshin-Yokohama Bldg 3F & 4F, 1-33-1 Hiranuma, Nishi-ku, Yokohama), welcoming families from Yokohama, across Kanagawa and central Tokyo. Our sister schools are YES Tokyo (Shibuya) and YES Odawara.

References

1. Byers-Heinlein, K., & Lew-Williams, C. (2013). Bilingualism in the early years: What the science says. LEARNing Landscapes, 7(1), 95–112. https://www.learninglandscapes.ca/index.php/learnland/article/view/Bilingualism-in-the-Early-Years-What-the-Science-Says (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC6168212/)

2. Hoff, E., Core, C., Place, S., Rumiche, R., Señor, M., & Parra, M. (2012). Dual language exposure and early bilingual development. Journal of Child Language, 39(1), 1–27. https://doi.org/10.1017/S0305000910000759 (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC4323282/)

3. De Houwer, A. (2007). Parental language input patterns and children's bilingual use. Applied Psycholinguistics, 28(3), 411–424. https://doi.org/10.1017/S0142716407070221

4. Cummins, J. (1979). Linguistic interdependence and the educational development of bilingual children. Review of Educational Research, 49(2), 222–251. https://doi.org/10.3102/00346543049002222

5. Cummins, J. (2008). BICS and CALP: Empirical and theoretical status of the distinction. In B. Street & N. H. Hornberger (Eds.), Encyclopedia of Language and Education (2nd ed., Vol. 2: Literacy, pp. 71–83). Springer. https://link.springer.com/rwe/10.1007/978-3-319-02252-9_6

6. Ministry of Education, Culture, Sports, Science and Technology (MEXT). (2017, published 2018). 小学校学習指導要領（平成29年告示）解説 外国語活動・外国語編 [Elementary School Course of Study commentary: Foreign Language Activities and Foreign Language]. https://www.mext.go.jp/component/a_menu/education/micro_detail/__icsFiles/afieldfile/2019/03/18/1387017_011.pdf

7. Government of Japan, Public Relations Office (政府広報オンライン). 2020年度、こどもの学びが進化します！新しい学習指導要領、スタート！ https://www.gov-online.go.jp/article/201903/entry-8992.html

8. Cambridge International Education. Cambridge Primary. https://www.cambridgeinternational.org/programmes-and-qualifications/cambridge-primary/ ; Cambridge Lower Secondary. https://www.cambridgeinternational.org/programmes-and-qualifications/cambridge-lower-secondary/