The board is scheduled to give final approval to rules governing the vouchers - authorized by the 2005 Legislature - at its meeting on Friday.

But Education Excellence Utah doesn't like a provision that limits which private schools can collect taxpayer-funded vouchers on behalf of students with disabilities who are home-schooled or who already attend private schools. The proposed criteria are less strict for private schools that accept voucher students who previously attended public schools, where they would have had an Individualized Education Program tailored to their needs.

"We're simply saying that the rule as proposed is illegal, and if they choose to implement it, we will challenge that," said Royce Van Tassell, the group's executive director.

His group's attorney, retained from the Salt Lake City firm Parsons, Behle & Latimer, filed a notice of intent to sue Friday at the state Office of Education.

The state board's attorney believes the rules are sound because they address language in the Carson Smith Special Needs Scholarships Act that says non-public school students can qualify for a voucher if they meet several criteria, including attending a "private school [that] specializes in serving students with disabilities."

"We've looked at it over and over and over, and we think the rule fairly reflects the legislation," Carol Lear said Friday. "It clearly says that 'schools specializing in students with disabilities' means something."

The rule defines "specialize" as schools with at least 80 percent of their students classified as students with disabilities or schools that are accredited and designated by the Northwest Association of Accredited Schools as "a school that meets the special educational needs of students under unique circumstances."

Few private schools in Utah have that specialty. Among them are the Carmen B. Pingree School for Children with Autism and Woodland Hills School, both in Salt Lake City.

Depending on the severity of a child's needs, the annual scholarships would range from $3,450 to $5,700, while kindergartners would be allotted $1,250.

The scholarship program targets children with at least one of the following disabilities: mental retardation; traumatic brain injury; autism; specific learning disabilities; serious emotional disturbance; or hearing, speech, language, visual, orthopedic or other health impairment. Five- to 8-year-olds with a developmental delay also qualify.