It is true that some people argue that a foreign language should not be one of the compulsory subjects studied in schools. While I believe it is useful for schoolchildren to learn a foreign language, I completely agree that they should not be forced to do so.
On the one hand, it will benefit the education of most children if they are encouraged to learn a foreign language during their school years. Firstly, through studying the language they will learn about the culture of that country, and some schools even arrange exchange visits, to enable students to weg briefly immerse themselves in the culture of the foreign country whose language they are learning. Secondly, children can access information in another language. For example, if they are studying English, they can enjoy websites which are only available in English on any topic in which they are interested. Finally, children can be encouraged to learn a foreign language through the range of enjoyable and fun materials available nowadays, especially interactive online learning.
On the other hand, it would be counterproductive to forcibly oblige schoolchildren to learn a foreign language. One reason is that children will not learn effectively through compulsion alone. They must be motivated to do so and this is only achieved through enthusiastic teachers who select stimulating language-learning activities. Another reason is that schoolchildren will be reluctant to learn a foreign language if they cannot see why it might be relevant to their present or future lives. For example, individual Vietnamese pupils should not be forced to learn English if they are certain that they will never need or want to use it in the future.
In conclusion, I would argue that schools should encourage, but not compel, children to learn a foreign language.