This quote addresses the question of Senator Wyden's reasons for opposing expanding the use of 529 plans to pay for primary and secondary education expenses, but does not address the OP's question at all, which was specifically about using 529 monies for homeschooling.

I was wondering about that myself. Did the Cruz amendment get introduced before the version which ended up passing? Or was his amendment an attempt to expand the private school language further, to home schooling? If it's the former, then the premise of the question is wrong to begin with.

@user4556274 Democrats opposed the amendment as a whole, both for homeschoolers and for private schools. They only managed to block the homeschooling part, though, as the result of the Senate parliamentarian's ruling regarding a technicality which raised the effective vote threshold to 60 votes for that one part, while it was only 50 for the remainder.

@user4556274 I edited the answer to address that part.

It's perhaps interesting to note that if you pare away the rhetoric, Cruz and Wyden more or less agree on the reason for the Democrats' opposition (taking Wyden's comments to be representative of the overall Democrat position). The Democrats have long opposed pretty much every measure that would tend to take money or students out of public school systems, as Wyden's comments demonstrate. They surely would reject Cruz's claim that they hate homeschoolers, but I don't think it's too far off that as a party, they hate that some people homeschool.

@JohnBollinger Oh, I agree with you completely. Honestly, if you've seen much of the vitriol that comes out of NEA in regards to those who don't attend public school - and especially against homeschoolers - the word 'hate' really isn't too far off. I've always been a bit puzzled by Democrats' arguments on that front. Their normal argument against voucher programs is that, if the average person could afford public school, only the poor would remain in public schools. If everyone who can afford to leave public schools would do so, what does that say about the quality of public schools?

"what does that say about the quality of public schools?" That they've been slowly strangled by neglect and lack of money for the last forty years?

@JoshCaswell Hmm... According to the National Center for Education Statistics (part of the Department of Education,) U.S. public schools actually spend more per student than average private school tuition.

I don't find Wyden's argument convincing, but it's the Democrats' argument so I will accept this. Thanks!

...which spending couldn't possibly be affected by resource-intensive students who private schools can refuse to deal with. And I'm shocked, shocked that the average for a single source of funding is lower than an overall expenditure. Did you know that passenger airline baggage fees are a fraction of a percent of what Fedex spends on average for one of their cargo flights? What on earth is Fedex doing with all that money?

@JoshCaswell Don't see current data, but, as of 1995, average spending for private schools was $3,380/student (NCES PDF, page 28), while public schools had an average of $6,146/student (NCES PDF, page 22). If you want to discuss this further, please ping me in chat. It's really straying from the topic here.

One thing nobody mentioned is the religious angle. Homeschools and private schools generally tend to be religious and many don't teach the scientific consensus on, e.g., evolution.

@k_g No one has mentioned it because it isn't relevant to answering this question (and also because it largely isn't true - most, if not nearly all, do teach evolution, whether or not they teach it as fact.)

@JoshCaswell there's no country in the world where public schools are better than private schools. None whatsoever. The more you pay, the better quality you get, end of story.

@JonathanReez But there are plenty of Public schools in some countries that are better than the Private Schools in others.

@Wren the biggest advantage of private schools is that the cost filters out the applicants, so your kid is guaranteed to study with kids of parents who care about their child. This alone is the biggest advantage, by far. The only public equivalent would be public schools for gifted children, which are not very common

@reirab people like Betsy Devos (one of the main pushers of private schools and vouchers) have said that this is part of a plan to bring religion back into American society.

@reirab and pretty much all homeschol in the US is fundamentalist Christian. Look up the ACE curriculum for some laughs followed by fears of the indoctrination suffered by anyone who takes it.

@reirab it's definitely on some Democrat's minds that private and home school == fake science, which is probably part of the reason they oppose private schools.

@k_g That's not the reason they stated. If you think that is the reason, please write your own answer (ideally with sources) rather than commenting on mine.

@JonathanReez what makes you think that parents who can afford private school care more about their kids than parents who can't? The only thing you know is that the people you go to school with have wealthy parents, nothing more.

@Erik those who can't afford it don't necessarily care less, but those who can afford it and do pay for it are usually the kind of people who have successful kids. And you want your kid to study with kids who are going to be successful. Statistically speaking its the quality of the childs peers that is the biggest indicator of future success in life.