Sponsoring Rep. Jim Ferrin hopes the changes will attract the moderate Republican votes he needs to land the measure on the governor's desk this year.
"The changes make it more politically sellable," the Orem Republican said Thursday. "The Senate has always supported tuition tax credits, and the House has always been the stumbling block.
"These changes make it more palatable for my colleagues."
The revised version will create a "means test" that gives the largest tax credit - perhaps $3,700 - to the lowest-income families and the smallest credit - $500 - to moderate-income families. Upper-income families would not be eligible for a credit, but that threshold has not been set.
The means test likely will be indexed to already established federal guidelines for free or reduced-price lunches in public schools.
Those guidelines are based on household income and family size.
Under the original bill, parents could claim a tax credit of up to $2,000, regardless of their annual income or tax liability.
"Even a $2,000 credit isn't necessarily going to turn the key for some of these low-income families," Ferrin said. "Upper income families really don't need any enticement."
The revised legislation also will include money to plug financial losses that school districts may incur as students switch to private schools.
In addition, it will require participating private schools to administer national standardized tests and share teachers' credential information.
Some of the changes resemble accountability provisions that West Jordan Rep. Steve Mascaro, one of those moderate Republicans, planned to incorporate into his own tuition tax-credit proposal. He wanted standardized testing and no reduction in school-district funding.
Right now, Mascaro said, no one knows whether tax credits will be good or bad for Utah.
"Everyone on both sides of the ledger continue to throw rocks at each other, and it's become apparent to me that the only way you will ever know if tuition tax credits work is if, in fact, it is tested," he said.
"Let's put it out there. If we find out it's not a positive thing, we should throw it away and never have to deal with it again."
Public school leaders acknowledged the significance of Ferrin's revisions, but said they still question its impact and practical application.
"Indexing and targeting low-income kids are two different things," said Charles Hausman, an assistant superintendent in Salt Lake City School District. "What does a $3,000 credit do for a family that earns $24,000? Not much."
Public-school advocates believe tax credits will drain money from schools and create a bigger divide between social classes.
"While some of these proposed changes might make a bad bill somewhat less damaging, our feeling is that it remains a bad bill," said Vik Arnold, the Utah Education Association's director of government relations."
Private schools also could have reservations about the reporting requirements that would be imposed on them if they chose to accept students using tax credits.
Clint Kirry, the Utah-based marketing manager for Utah's six private Challenger Schools, has mixed feelings. While he supports the idea of parent choice and thinks a tuition tax credit will foster increased opportunities, he wants to be sure private schools don't fall victim to government regulations.
The testing requirement wouldn't be a big deal for his schools because they already administer the Stanford Achievement Test, and officials are proud to share - even publish - their high scores.
"It's a selling point," Kirry said.
As for sharing whether teachers hold state licenses: "If the bill requires us to disclose our credentials, and simply disclose them, we're fine with it," he said, pointing out that Challenger independently credentials all teachers.
"But if it begins to require certain certification, we've lost our ability to be a private school, so we wouldn't support that."