By now it's well-understood, despite the best efforts by rent-seekers and left-wing ideologues (who've even duped the ACLU--more on this at a later date,) that education is not only not a public good in the proper sense of the term, but that government provision of education causes market failure. Simply put, not only is there no strong rationale for government provision of education, other than inertia, but the practice is harmful, preventing the development of more desirable alternatives.
To a large extent this is the fault of a double-payments problem. Parents who, all things being equal, would send their children to private school X, will instead, having already paid taxes that fund the local public school, decide to send them there, either because the perceived difference in quality isn't high enough to merit paying twice for education, or because they simply can't afford both the tax and tuition.
The solution--and the just thing to do--would be to provide dollar-for-dollar tax relief, up to the amount spent per pupil at the local public school or the payer's total tax burden (whichever is less), to parents, grandparents, godparents, neighbors, strangers, or whoever else will pay for all or some of the private education of an individual child. In one of its more bizzare moments, however, the legislature instead decided to offer a tax credit, with an arbitrary cap, for contributors to charitable scholarship-providing organizations.
While, for its day, it was a groundbreaking measure, the tax credit program didn't come anywhere near the heart of the issue; it didn't provide tax relief to actors in the education market removing the State's, and by extension the taxpayers' responsibility for the schooling of a particular child.
HB2218 provides direct tax relief to homeschoolers, whose role in the still-stunted education market wasn't even taken into account when the original tax credit bill was passed. Parents relieving the State of its burden by taking their children's education into their own hands will in turn be relieved of some of their tax burden. That's called justice, and it makes economic sense.
Call or write your representative and ask him to support HB2218. While you're at it, call the bill's sponsors and ask them to extend its scope to parents paying someone else to teach their children. With the legislature taking steps to at least partially fix the education market and the public now comfortable enough with choice that 62% support vouchers and 55% say all students deserve private-school scholarships, the time is right for Arizona to fix the double-payments failure for good and reclaim its position as a trailblazer for education reform.