Public money does not go to private schools. It goes to parents to choose a school.
In 2015 the NC Supreme Court ruled specifically on our Opportunity Scholarship, that the North Carolina legislature can use its general revenue fund to create educational programs outside the public-school system (Hart v. State of North Carolina et al). How does the concept of school choice measure up to constitutional scrutiny?
Separation of Church and State vs. Right to Religious Assembly
The phrase "separation of church and state" isn't actually in the constitution--state or federal. It simply describes a part of the first first amendment , which says "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof." While the government can't have a formal relationship with a given religious institution, it also can't inhibit its citizens to practice the religion of their choosing. But in North Carolina--only affluent families could afford to exercise their constitutional right to religious assembly by sending their children to religious schools (private schools). Opportunity Scholarships provides a measure of equality for low-income families to also exercise religious assembly.
The idea that the Opportunity Scholarship Program gives public dollars to religious organizations would constitute a formal relationship between church and state—but its parents who determine where this money is spent; citizens exercising their right to assemble. In fact, giving parents the means to determine the education of their own children constitutes a check-and-balance on the powers of government. Should government impose educational values, or should it be founded on the will of the people—in this case—parents?
The section of the North Carolina State Constitution dedicated to education, opens with “religion, morality, and knowledge” as the foundational values for which education is encouraged in our state. In a capitalist society, “means” is money. The root of the argument is whether to give families the “means” to determine education that results in mankind's "happiness" and "good government", or giving government the “means” to impose an education that the government deems necessary for “good government,” and your "happiness."
The argument that educational options result in differing educational quality from school to school, in defiance of Article IX, Sec. 2 of the NC Constitution, citing “uniformity,” students in poor areas will tell you their school’s academic quality differs from students in other zip codes. In the same section, the use of the word “opportunities” is multiple, implying choice.