Mexican immigrants used to have higher-than-average levels of education, but today the average male Mexican migrant has lower-than-average education by Mexican standards...
A better immigration policy would tighten the border, while allowing in more legal immigrants from Mexico and other Latin countries, and require higher levels of education. Young Mexicans would see greater reason to invest in education, to the benefit of all Mexican society, not just those who cross the border.
I thought that the immigration topic was "a well-squeezed orange," as the late economic historian Charles Kindleberger used to put it, referring to subjects where he doubted that there was much new to say. But Tyler manages to say a lot of new things in his piece. It is a very worthwhile read.
However, I winced at the sentence, "Shutting the Mexican border... would paralyze American businesses and agriculture." The word paralyze is far too strong, in my opinion. I would have said require adjustments in instead. I suspect that unskilled labor is a factor of production for which substitution is not terribly difficult.