My reply will be nuanced.
The newcomers already have varied schooling levels in their original languages. If someone never went to school in his country of origin, it will take a long time before he learns the rudiments of the language and is functional in the new one. However, someone who holds a doctorate from China and has never learned French will learn it quickly if he is in a full-time course. Unfortunately, it's not always possible because the newcomers also have to earn a living while they do this.
Our organization offers evening courses, but that it still part-time, and the means are not adapted. That is the heart of the issue. We have to modernize language learning.