I really don't understand why you think the English (writing and reading skills) is so difficult for Chinese kids growing up in Canada and what kind of level of English you expect of from your kids.Keep in mind, language is only a tool to communicate. Most kids won't become English writer, linguist or translator, which certainly demands a high level of proficiency in English. Look around the country you are living in, a lot of French Canadians without perfect English (based on your standard)and having strong accent could still outperform in a variety of professions like law, business and politics ( ministers and Prime Ministers) etc.