In countries where English is not the first language, many parents and communities believe their children will get a head-start in education by going ‘straight for English’ and bypassing the home language. However, as Professor Kioko points out, the evidence suggests otherwise.
Source: https://www.britishcouncil.org/voices-magazine/why-schools-should-teach-young-learners-home-language

 

Intellectual: Students need uninterrupted intellectual development. When students who are not yet fluent in English switch to using only English, they are functioning at an intellectual level below their age. Interrupting intellectual development in this manner is likely to result in academic failure. However, when parents and children speak the language they know best with one another, they are both working at their actual level of intellectual maturity.

Source: http://www.idra.org/IDRA_Newsletter/January_2000_Bilingual_Education/Why_is_it_Important_to_Maintain_the_Native_Language?/

 

“Decades of research indicate that children should be educated in a familiar language—most times, that is the language of the home or community” … Also, research makes clear, children can learn to read well in a new language only if they have a strong foundation of literacy in their first language because of the “transfer” of skills from one language to another

Source: http://www.air.org/resource/language-learning-and-literacy-native-tongues-first