Does forcing students to speak English in school affect the students' knowledge of their native language?

Question

In places where I live some private institutions are forcing students (of age 6 to 17) to speak only in English, regardless of their native language. This restriction is not only placed in English class but on the entire school premises, except other language classes. The purpose of these restrictions are to help students improve their English. Also, these institutions fine and punish students who speak in the native language within the school.

Some activists have claimed that the punishments will make students think ill of their native language and make them stop speaking it elsewhere too. I too think that could happen as children spend a great deal of time in school. Also, they claim that their vocabulary and fluency in their native language will be reduced.

I saw in a similar question that forcing students to speak in a language helps students to acquire knowledge of a second language. But will it affect their knowledge of their native language? Will it reduce the fluency and vocabulary in one's native language?

Answer 1

In the specific case of students being forced to speak English in school, I would say no, students will still retain their full vocabulary and knowledge of their native language (L1).

For one, it's only in school that English is mandated to be spoken. At home, in shops, and almost anywhere else, the L1 will be spoken (unless people are more comfortable with English). In addition, you mentioned that there are often language classes in school that teach the L1. Each student is likely required to take one of these classes, so this ensures that fluency in the L1 does not decrease over time. Finally, remember that school only lasts for 12 years, with several weeks or months off during every school year. The majority of the time not spent in school is time that is used to refresh the L1.

The only downside to this system, as you point out, is that students may think less of their L1 because they are not allowed to speak it in school. However, this mentality should not hinder their performance in their L1.

Answer 2

Oh yes it can. (Source) For some people in America, learning English means they go through subtractive bilingualism, where they learn English at the same time they lose their native language(s):

Specifically, this article deals with the phenomenon of "subtractive bilingualism," the name given the problem by Wallace Lambert who first discussed it in relation to French-Canadian and Canadian immigrant children whose acquisition of English in school resulted not in bilingualism, but in the erosion or loss of their primary languages

This phenomenon has been quite a while actually but is well ignored by researchers. Though this is really the only viable source I can find, I will give my view on this as well.

It depends how they are being taught. Some people talk English at school and their native language at home, allowing for continued fluency and retention of their original language. Others only talk English for prolonged amounts of time without using their native language, causing the slow erosion of the language. Some might even face the effects of subtractive bilingualism. But in school, due to lack of fluency at first, teachers should also be able to speak in their native language to convey instructions at ease temporarily until they can understand basic and maybe advanced English.

Answer 3

There's an important ambiguity in the question that makes me somewhat unhappy with the accepted answer (so I'm providing an alternative here). Here's some clearer variations on the question:

1. Will forcing students to use L2 at school from T1 cause student's knowledge of L1 to fall?
2. Will forcing students to use L2 at school from T1 cause student's knowledge of L1 to be lower than if L1 was used in school?
3. Could the use of L2 in school cause students to not reach adult fluency in L1?

I think fi12's answer is generally correct with respect to 1. If the only context where L2 is used is school, then L1 will not fall. (If for other reasons, L2 becomes prevalent in all contexts of life -- e.g., a Japanese family living in America, sending their kids to American schools, where they have English-speaking friends and clubs, then it's possible that L1 will fall).

In general, the answers to 2 and 3 are going to be that yes L2 instruction will retard fluency in L1 for academic contexts and will make them worse at the language than if they also used it at school.

A second scenario could be where L1 and L2 are closely related (like some dialects of Chinese) and instruction in L2 at school breaks local usage down.