WASHINGTON — Kendra Espinoza sends her daughters to Stillwater Christian School, in Kalispell, Mont. The girls are thriving, but the tuition bills are steep. Ms. Espinoza, a single mother, has worked three jobs, raffled off quilts and held yard sales to help make the payments.

She had also hoped to get some money from a state program enacted in 2015 “to provide parental and student choice in education.” Soon after the program started, though, a state agency said students attending religious schools were not eligible.

Ms. Espinoza and two other mothers with children at Stillwater sued, and the Montana Supreme Court ruled against them, shutting down the entire program for all schools, religious or not.

The court relied on a provision of the state’s Constitution that bars the use of government money to aid religious schools. Many state constitutions have similar provisions.