A woman who says her oldest child thrived in Roman Catholic schools after struggling in Indiana's public education system defended the state's broad new voucher law Thursday, saying it provides opportunities to send children to appropriate schools their families might otherwise be unable to afford.

Heather Coffy, one of two Indianapolis women seeking to help defend the Indiana program against a legal challenge, said her son Delano was flunking out of a township public elementary school in fourth grade before she moved him to St. Monica's Catholic School on the Indianapolis north side. She said his transfer to a better learning environment helped her son grow.

"It was amazing: his demeanor, his attitude, his confidence, his grades. It was like night and day," Coffy said at a courthouse news conference as her two younger children, sixth-grader Darius Coffy and third-grader Alanna Marshall, looked on. Delano was on a basketball trip before the start of his freshman year at Bishop Chatard High School.

Coffy and Monica Poindexter, the mother of another Indianapolis Catholic high school student, filed a petition Thursday seeking to intervene in a lawsuit filed by union teachers, administrators and clergy challenging Indiana's new voucher program. The two women are represented by the Institute for Justice, an Arlington, Va.-based school choice advocate that says it has helped defend voucher programs like Indiana's in other states.

The lawsuit filed earlier this month in Marion County seeks a preliminary injunction on grounds that most of the private schools whose students are eligible for the vouchers are affiliated with churches or other religious institutions. It also said the Indiana Constitution directs the General Assembly to educate children through a "general and uniform system of Common Schools."

Indiana's program will be limited to 7,500 students this coming school year and 15,000 next year, but then there will be no limit on the number of children who could enroll as long as their parents fall within income limits. Families of four currently earning up to about $60,000 a year could receive them.

As of Thursday, nearly 800 Indiana students had been accepted into the program, and nearly 200 private schools had been approved, said Alex Damron, a spokesman for the Indiana Department of Education.

They include Coffy's two youngest children. The voucher application for Delano Coffy was pending.

The actual value of the vouchers is based on a sliding scale and less than the amount of tax money a public school would have received for that student. The maximum value for students in first through eighth grade would be $4,500.

The Indiana State Teachers Association, the state's largest teachers union, has said the new law could cut funding to public schools by up to $65.8 million.

"It's not about school choice," ISTA President Nate Schnellenberger said Thursday. "It's about taking public tax dollars that have already been budgeted for public schools and moving them to private schools."

Even before the voucher law, students could attend public school in another district as long as there was space and as long as it was the new school district's policy to accept students from outside its boundaries.

Coffy said she never took advantage of that option. When Delano struggled, other parents advised her to try St. Monica.

"I'm a firm believer that every child has the right to the best education, period. I also want people to understand that school choice is not about a free ride," she said, noting vouchers won't cover all of her children's tuition. She also must arrange transportation for them to and from school.

"I did not choose a Catholic school based off religion," said Coffy, a non-Catholic. "I based it off of the quality of education, the environment, the small classes, the attention that was going to be given for all of my children, and every student that is enrolled in private schools. I think that's what it's all about."

Bert Gall, an institute for Justice attorney, said Indiana's voucher program gives lower-and middle-income families "true education choice."

"The same options that better-off families in Indiana have should be enjoyed by everyone, and this program gives everyone a chance to do just that," Gall said.