Worth specifying that this also applies to the "good" immigrants such as the Poles, not just the much vilified Muslims. The kids of Polish immigrants really struggle. And if you go a generation back, the Vietnamese boat refugees had similar issues: their kids really had issues, there were Vietnamese criminal gangs in Oslo in the 90s. The ex-Yugoslav organized crime groups were maybe more notable in that they were often first generation, but they're mostly a memory too by now. Then there's the "hapas", children of Asian women who immigrated by marrying native men. Scandinavia hasn't seen much trouble with them - yet. But I think there's some danger here, online I've seen some worrying communities.

I think identity rootlessness is an underestimated factor in immigration woes. Youth of all kinds can often be exploited into adopting a destructive self-identity, but some groups are more vulnerable. One notorious Swedish gang actively recruits from the foster care system.