The tax credit program, which would provide scholarships to K-12 students to pay for private schooling, would mark a significant shift in federal education policy. The scholarships would be the first major federal initiative designed to propel the nationwide growth of private school choice, a largely conservative and Christian movement championed by President Trump and suburban Republicans alike. It comes just as the Trump administration dismantles large parts of the U.S. Department of Education that support public schools attended by the vast majority of 50 million students.

The private school choice movement, which started in 1990 to give families more options aligned with their values and children's learning needs, remains a small piece of the education landscape. It supports about 1.2 million students in private and home schools in 35 states, primarily in the South and West. Advocates expect that the proposed federal program would jump-start a new round of expansion by providing scholarships to families to make private school more affordable.

Beyond boosting participation, the program is also a wedge to crack into states controlled by Democrats. These blue-state lawmakers, backed by teachers' unions, have long resisted private school choice as a threat to public school enrollment. The granting of scholarships, advocates say, would plant a seed of interest among families in Democratic enclaves at a time when enrollment and academic performance have been steadily declining at public schools.

"In terms of the number of students served and the geographic scope, it would be the most important piece of school choice legislation ever," said Patrick Wolf, a prominent scholar of the movement at the University of Arkansas. "Advocates hope it will provide a proof of concept in blue states and show that if a few thousand kids get scholarships the public school system won't crater."

But the potential of the scholarship program to meet the advocates' goals has been weakened this week in the Senate. The program was included in the massive budget bill because, as a standalone measure, it wouldn't survive a filibuster by Senate Democrats. The budget bill can be passed by a simple Senate majority, provided it only addresses fiscal matters.

The Senate parliamentarian, however, objected to the scholarship program, ruling, to the dismay of Republicans, that it seeks to impose a policy on the states. In response, Republicans had to amend the initiative to allow states to decide whether to participate, a change that could hamper the movement's efforts to breach liberal jurisdictions.