The United States Constitution mentions the word "religion" exactly one time, and that is in the First Amendment of course, whose first two clauses read:

"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof . . ."

This means that no federal court (including the Supreme Court) may rule on religious matters--unless it is in the case of a law the the US Congress has passed.

The Founding Fathers left these matters to the states. Although it is the correct ruling, the fact is that it is unconstitutional for the Supreme Court to even consider this matter. It's a case for the Maine State Courts to decide.

https://www.ncregister.com/cna/us-supreme-court-rules-against-maine-s-ban-on-tuition-aid-to-religious-school