Under a substitute bill to be released today, the tax credits would no longer be off-limits for parents whose children already attend private schools.

That could alleviate critics' concerns about discrimination, but it also could be a pricey change. A forecast from the Legislative Fiscal Analyst's Office of the cost implications won't be available for days.

"The change has eliminated what I saw as a major constitutional issue, but we've got to see the fiscal note to see how much that's going to cost," state school board Chairman Kim Burningham said.

The revised House Bill 39 will be available for public review during a news conference this afternoon.

Among its biggest changes is the opening of the tax-credit benefit to any parent sending a child to private school - not just parents who transfer their kids from public to private schools.

Sponsoring Rep. Jim Ferrin, R-Orem, said it is no longer necessary to exclude current private-school families from tax credits now that the measure includes a so-called means test that awards larger tax credits to lower-income families.

That means the parents of 15,000 students currently enrolled in private schools could qualify for tax credits if they meet family income qualifications.

"I would guess that most of those families won't qualify. It's still means-weighted, so it still depends on economic circumstances," Ferrin said. "I'd rather discriminate against students based on economics rather than when they enrolled."

The revised version would create a sliding scale that gives the largest tax credit - $3,700 - to the lowest-income families and the smallest credit - $500 - to moderate-income families.

The means test will be indexed to already established federal guidelines for reduced-price lunches in public schools. Those guidelines are based on household income and family size.

A family with a household income at or below the federal guidelines would qualify for the full $3,700 credit. A family with a household income at 275 percent of the guidelines would qualify for the $500 credit. Incomes beyond 300 percent would be ineligible for the credit.

For example, a family of five with an annual income of $40,756 would get the full credit. A family of five with an annual income of $112,000 would get the smallest credit.

"I don't call $112,000 a 'means test,' " Burningham said. "Try telling that to teachers. They'd laugh me out of here, and justifiably so."

Ferrin says it's a bargain, even at the upper income levels.

"Do we pay 100 percent of the cost of educating that child or $500?" Ferrin said. "To me, it's still a great deal."

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.

Under the original bill, parents could claim a tax credit of up to $2,000, regardless of their annual income or tax liability.

rlynn@sltrib.com