Usual disclaimers: I am not a lawyer. This is very much a lay understanding of what's being sorted out here.
The Supreme Court released their decision in Carson v. Makin yesterday, causing a good bit of concern, distress, and words of warning in the education universe. I think we need to answer two questions: what was decided, and how much do we in public education need to worry?
In understanding the case, you first need to know that Maine doesn't run public schools in every school district; about half the districts in Maine don't have a secondary school. The state has had a long tradition, then, of instead providing tuition to a school of the family's choice for secondary school. This means the state effectively then has a voucher system for much of secondary education. Until 1981, this included religious schools; in 1981, the Maine attorney general opined that public funding going to private schools was a violation of the Establishment clause, that is the First Amendment bar on Congress making any law "respecting the establishment of religion." The state then required that any state receiving the tuition payments from the state needed to be "a nonsectarian school in accordance with the First Amendment of the Constitution."
Two families brought suit. The majority (Roberts, writing, Thomas, Alito, Gorsuch, Kavanaugh, Barrett) found for the plaintiffs; Breyer wrote the dissent in which Kagan joined, with Sotomayor joining all but one part (that starts on page 23 of the link above); she filed a further dissent spelling out her objections to that piece (that starts on page 41).
I think the best way of explaining how the majority got there is what both Breyer and Sotomayor note in their dissents: the Establishment clause is held in tension with the Exercise clause which is the "prohibiting the free exercise of" phrase that follows in the First Amendment, but the majority breaks this tension and puts the Exercise clause over the Establishment clause. Congress can't make a law about religion; they also can't prevent people from following their own religion. Effectively, SCOTUS found that by not sending the tuition payments to religious schools, the state was not neutral. Roberts writes, "The State pays tuition for certain students at private schools--as long as the schools are not religious. That is discrimination against religion." (p. 10)
I have to be honest: it's hard for me to believe how just...dumb that statement is. What it is in fact is the state refusing to support religion, which is a principle as old as the Republic, and with good reason. Both Breyer and Sotomayer put this better than I have here, and I recommend reading the dissents if that's of interest.
Roberts and the majority have rested much of their argument on the 2017 Trinity Lutheran v. Comer case, which you may vaguely remember had to do with playground resurfacing (no, I am not kidding); the church preschool sued because they couldn't get public funding for their playground resurfacing, and SCOTUS found for the church. There's been an attempt at a distinction between if the funds are being used for religious instruction, but it's clear that many of the schools in question--as it is their point!--infuse their religious perspective throughout their curriculum.
What then does this impact?
At this time, the case and its impact rests on state tuition payments to private schools, or vouchers. Thus it is the states that have vouchers that may need to shift. Matt Barnum on Chalkbeat noted that most states that have vouchers already allow for state funding to go to religious schools.
Coverage from Bangor notes that this then needs to be sorted out with anti-discrimination laws in Maine, as it is a teaching of some of the religious institutions in question to discriminate against, for example, LGBTQ students or families.
What it does not do is require the creation of vouchers; as Chalkbeat has:
Critically, the decision does not require states to offer public funds to private schools. In his majority opinion, Roberts reiterated something he wrote in the 2020 case: “A State need not subsidize private education. But once a State decides to do so, it cannot disqualify some private schools solely because they are religious.”
Thus, this decision does not impact Massachusetts, for example, which is a non-voucher state.
However, Breyer (who doesn't have straight vouchers and charters in his dissent) does note the question this raises about charter schools that want to be religious schools, or religious schools simply flipping to being charter schools. Then they don't require vouchers anymore. That big mess was covered back in February by Chalkbeat. There was some discussion of this on Twitter yesterday; check on the school finance list I keep for some of that back and forth.
But that sick feeling in your stomach over the breakdown of church and state being separate in the U.S., stemming from a healthy concern over the religious wars of Europe? Me, too.