You make some excellent points here.
Up until the beginning of the illegal worker invasion, most of the seasonal agricultural work was done by young men ages 15 - 18 during summer break.
(In fact, that is why we have a summer break to begin with, so that children could stay at home and help bring in the crop harvest.)
Now, the only thing we are harvesting in this country (besides the lettuce, corn, chicken, peanuts, etc.) during the summer is gang murder and millions upon millions of illegal workers.
Speaking of the legality of not hiring a native American youth under 18 ~versus~ hiring an illegal immigrant - really makes one wonder who is BULLCHITTING who is this country!
You make a couple of great points...the cascading effects of a group of hormone charged American youths being locked out of bone-wearying summer labor and having few options for productively channeling that energy & time. The results are milling around in malls & exhibiting pack behavior.
And the point about the legalities on one hand & illegalities on the other--Yup, I strongly suspect that the forces that be don't want the current situation changed one iota. The illegal laborer is kept in line (from the employer's standpoint) by the fact that he is illegal and that legitimate issues about safety, overtime pay, etc. go unchallenged.