How to make a country suffer?

Fernanda Santos writes in the NYT: 

Since the bill cracking down on illegal immigration was passed by the State Legislature in May 2010, enrollment at the Balsz Elementary School District here in Phoenix, where 70 percent of the students are Hispanic, has dropped by 8 percent, and fewer parents volunteer to walk children to and from school, the superintendent, Jeff Smith, said.

Immigration is self-selection. That is not well understood.