According to Edweek, Congress's proposed tax plan would allow families to pull up to $10,000 a year out of their 529 college savings account and spend it on K-12 private school tuition (as well as other educational expenses). The proposal appears to be more an act of desperation than rationality in pursuing public support for private choice in K-12 education. The Trump administration's earlier proposal to take federal funding for public schools and drive it toward vouchers and charters never got any serious traction. If anything, DeVos's support for privatizing education made that proposal less popular with the public.
Education Law Prof Blog