The main issue is integration, not immigration. City planning and free school choice plays a big part imo. If most immigrants from poor countries end up living in the same areas and having their kids go to the same schools as each other, then you'll inevitably end up with situations like this.
And I'm sure the archaic drug legislation and a few details about the court system play a part too.
And I'm sure the archaic drug legislation and a few details about the court system play a part too.