“I believe changes to the 529 plan have been proposed to allow them to be used for secondary education, but I don’t think that is in effect yet.”
Yep, they are in effect. Up to $10,000 per year can be withdrawn for primary and secondary education, presumably including organized academic camps and online courses, starting in 2018. There had been a provision to allow homeschool parents also to access funds, but that was stripped out on a Democrat challenge late last year.
This article focuses on the implications for financial aid and also the likelihood that private schools might simply raise tuition in order to capture the savings. That makes sense to me, but only on a medium term basis. Should be a benefit for the next few years on a net basis I would think for those who have overfunded 529 plans.
https://www.nytimes.com/2017/12/21/your-money/529-plans-taxes-private-school.html