First, this somehow assumes that immigrants aren't doing well enough. And what - poor people should speak the local language at home just in case it improves their economic standing, even though it would lead to missing a lifelong benefit for the children. But if you are already doing well, don't?

If you don't keep poor people suffering like folks do in the US, being poor isn't as big of a detriment and the adults are perfectly able to improve on their own time. And it isn't like being an immigrant means you are poor.