Utah residents can avoid huge property and income tax increases over the next 15 years if voters approve the private school voucher program, according to a report commissioned by the Utah Taxpayers Association.

Critics of the proposed voucher plan, however, say the report commissioned by the Taxpayers Association is biased and wrong. If anything, they say, Referendum 1 will lead to increased taxes.

If approved by voters on Nov. 6, the voucher program would provide families with a private-school tuition voucher, ranging from $500 to $3,000 per student, based on parents' income. It also would appropriate $9.2 million for mitigation money to ease the impact on public schools for five years after students leave and go to private schools.

According to the Taxpayers Association report, Utah's public school enrollment will have grown by more than 150,000 students by 2016. The past decade saw growth of about 50,000 students.

The outcry this year over increasing property taxes will pale in comparison to the outcry that will erupt when taxes double to fund an influx of students into public schools over the next 15 years, said association vice president Royce Van Tassell.

"This is small potatoes," Van Tassell said.

The association's sister organization, the Utah Taxpayers Foundation, commissioned the study by Aspire Consulting this year to analyze and project student enrollment through 2022.

"We think Utah voters need to appreciate the impact of diverting some of that growth in public schools into private schools," Van Tassell said.

Van Tassell said 20,000 students could switch from public to private schools over the next 13 years and that would represent a savings of $50 million a year to the state.

It may not be a surprise to see the Taxpayers Association come out in favor of vouchers. The association's president is Utah Sen. Howard Stephenson, R-Draper, who voted for the law and co-chairs the Legislature's Joint Public Education Appropriations Subcommittee.

Van Tassell is the former spokesman for Parents for Choice in Education, a pro-voucher group.

But voucher critics say the report is wrong. "Their base assumption is wrong," said Lisa Johnson, spokeswoman for Utahns for Public Schools. "Utah does not spend $7,500 for every student."

She said some students cost more, some less, but according to state and federal sources, the 2006 per-pupil expenditure in Utah was $5,397.