The Con Con delegates, who arranged themselves not by party but alphabetically, were so preoccupied with the public interest that they agreed public funds could be spent only on public agencies. During deliberations on the no-aid clause, the pastor of Helena’s Plymouth Congregational led the charge of “preserving our public school system,” preaching, “that’s what this issue is all about. I don’t think we ought to dilute that in any way.” (Diluting that is the aim of Espinoza.)

Article X, Section 1, of the ’72 Constitution proclaims that it is the duty of the state to “develop the full educational potential of each person.” That is an expensive ideal in a desolate wasteland. Public schools are supposed to be a volume business, but tell that to the Great Plains. The state of Montana has about 60,000 fewer inhabitants than the number of students enrolled in New York City’s public school system. I have volunteered in that epic system, which is to say I have had to excuse myself from a struggling student to go cry in a bathroom, so I sympathize with an urban kid who might eye a parochial school as her best chance.

That school choice logic doesn’t apply to Montana, where the poorest schools often have the smallest class sizes. The Montana Free Press reported that out in Prairie County, “Terry High School’s sophomore class has just five students this school year.” Starting in first grade, my friend Genevieve would ride her horse Croppy to the Malmborg School near Bozeman Pass; one year she and her brother Pete were half the student body.

When USA Today asked Ms. Espinoza if she had any qualms about what her case could mean for public schools, she insisted, “They have plenty of money.”

How I wish that were true. Last year, the public school district in Kalispell announced $1.7 million in budget cuts, Great Falls recently lost almost a hundred teachers, and Billings just announced about $4 million in cuts that mean canceling fifth grade orchestra and band.

A Supreme Court decision on Espinoza is expected in June. If the justices rule against Montana’s voters, tax credits for private school scholarship donations could surge. Revenue that might revive the Billings fifth grade band program could underwrite the fifth grade band at a pricey Kalispell private school.

Kalispell is the seat of Flathead County, which between 2000 and 2015 added more than 15,000 jobs just as rural Chouteau County was losing more than 300. Overturning the no-aid clause will shovel more money into the cities (where most of the private schools are) and kick Chouteau while it’s down, thereby thwarting the framers’ plan to spare needy districts from taxing “their residents three or four times as much as rich districts to provide less than half as much money per student.”

The public schools the framers conjured ask the taxpayers to splurge on fairness, not privilege, to pull together, not away. That beekeeper, those clergymen and moms chartered a state in a republic where a first grader on horseback is supposed to be as big and important as the mountains. As the Supreme Court justices ponder whether to upend all that over what appears to be a $150 trifle, I’ll pass along this lesson of Montana winters: A collapsed roof starts with a single snowflake.

Sarah Vowell, a contributing Opinion writer, is the author of “The Wordy Shipmates” and “Lafayette in the Somewhat United States.”

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