It's not necessary to point out that Cal Thomas is himself about as rigid as they get, suffering as he does from ideological rigor mortis.  

But he make this misleading statement: "Many on the left believe school choice should not be available to poor children, not because school choice is a bad idea but because the Democratic Party doesn't want to alienate teachers' unions that oppose it."  

The issue here is the survival of public education as it has existed for over a century.  "School choice," in practice means a free-for-all sort-out according to income and, for the poor, place of residence.  More enabled chldren quickly gravitate to better performing schools, leaving the public schools, who have no choice about the students they will accept (as charter schools do), to take the social and academic problem kids.  Better teachers naturally gravitate to a better class of student, so the public schools also end up with the worst teachers.  In short, dump those who need help most.