Here's a twist on the legal debate over school voucher programs. Maine has a school voucher program for people from small towns that don't have public schools, a program that goes back over a century. In 1980, however, the law was amended to forbid the vouchers from being used at religious parochial schools. A suit was filed claiming that this was religious discrimination, but the Maine Supreme Court upheld the law in April. The plaintiffs have filed cert asking the US Supreme Court to hear the case. It will be interesting to see if the Court agrees to take the case.
The two obvious precedents here are Zelman v Simmons-Harris (2002) and Locke v Davey (2004). Zelman upheld an Ohio voucher bill and said that the state may allow vouchers to be used for religious schools as long as the choice was made by the parents, on the grounds that a generally applicable benefit may be used for a religious purpose without violating the establishment clause (for instance, food stamps may be used to buy food to make a Seder meal, or an Easter dinner).
Locke, on the other hand, involved a Washington program that awarded scholarships to students based on merit, but prohibited them from being used in any "devotional" program such as studying for the ministry. So under existing precedent, the rule is that states may provide vouchers that are used for religious schools, but they don't have to do so, they can limit their use to non-religious schools. It will be interesting to see, if cert is granted, whether the Court will overturn Locke.
The makeup of the controlling rulings in those cases may be important here. Interestingly, both of those precedents were written by Chief Justice Rehnquist, but with very different concurring majorities. In Zelman, a 5-4 decision, the majority was Rehnquist, Scalia, Thomas, O'Connor and Kennedy (generally, the 5 most conservative justices on the court at that time). But in Locke, it was Rehnquist, O'Connor, Kennedy, Souter, Ginsburg, and Breyer in the 6-3 majority, with Scalia, Thomas and Stevens in dissent.
In the Locke decision, Rehnquist said that forbidding the use of such funds for religious instruction, even if the benefit is given for an entirely secular purpose and the choice of how to use the funds is entirely up to the individual, not the government, falls into the "play in the joints" between the establishment clause and the free exercise clause. It was a typical Rehnquist opinion, based on very narrow and technical grounds. It will be very interesting to see how the Roberts court handles such cases.
One of the key questions is, does Maine have a "Blaine" amendment to its constitution? According to Wikipedia, they do not have one.
It might be hard to believe that James G. Blaine's home state would not have such an amendment. One of the issues in Locke (if I remember correctly) was that Washington has an amendment in its constitution that prevents the use of state monies to support religious schools and education. Several states passed such amendments around 1900, perhaps with anti-Catholic animus, perhaps with other goals in mind. That affects what has been done historically in the state, and historic precedent is one of the favorites of the Court (think of the Texas 10 Commandments monument and Kentucky's newer actions).
Washington has a Blaine amendment, Maine does not. How does that turn the case?
(Look for "blaine amendment" at Wikipedia for background)
Maine does not have a Blaine amendment, but that should be irrelevant in a Federal court case. The Federal court would only consider whether the legislation violates the US constitution, not the state's constitution. So that really shouldn't have any effect on the outcome at all.