This is just an anecdote - but a telling one none the less. A friend of ours teaches English in local schools here on the Riviera. One of the schools/classes she teaches is made up heavily of the children of North African immigrants to France. She had two interesting comments about her expereinces with these children while we were discussing her job and how as a part-time assistant teacher she earns little more than minimum wage for the hours she works.
The first comment was that the vast majority of immigrant children showed no interest in learning English. Now it is true that in France English is clearly a foreign language so learning English isn't exactly critical but, on the other hand, here on the Riviera the main industry is tourism with many tourists from the UK and other parts of Northern Europe, not to mention semi-permenant expat residents such as me and my wife. If you want to work in any tourism related field or get a decent job in Sophia, where all the high tech companies are, then you have to speak English. Not speaking English immediately limits your job prospects and potential salary.
The contrast between this attitude and the attitude of many Indian or Chinese immigrants to the UK (the only other immigrants I know relatively well), is staggering. The children of these Asian immigrants are pushed the way that I had thought was limited to urban legends about E Europen Jews in Brooklyn whereas the French North Africans seem to have no push what so ever. Unlike the Asians whose children are attend university and earn top salaries in white collar professions, these North African children will be relegated to low-skilled jobs that require no communication with foreigners. Given that most of these jobs are precisely the ones that are most easily outsourced abroad or replaced by machines their future prospects as contributing members of society seem to be limited.
The second comment was that these children don't think of themselves as French. During one class she asked them where they came from and the replies were "Tunisia" or "Morocco". The (French) teacher apparently laughed at that and said "no no really they are all French even many of their parents were born in France". If second generation immigrants don't see themselves as French then the country has a big big problem. Again I think back to the Asian immigrants in the UK who all say they are British and who can joke about how people never know whether Satinder is male or female.
If you wonder why many of my French neighbours have sympathy for the fascist Le Pen then this would probably explain it. If the immigrants don't see themselves as French, don't seem to care about education or working then is it any surprise that others want to send them "back"?