Florida's largest school-voucher program is unconstitutional because it redirects taxpayer money to religious schools and creates a separate system of state-funded schools, according to a lawsuit filed Thursday in Tallahassee by the teachers union and others.

The lawsuit challenges the Tax-Credit Scholarship Program, which this year is expected to pay private-school tuition for nearly 70,000 students from low-income families. About 70 percent of the participating private schools are religious.

The program is a "risky experiment," said Joanne McCall, vice president of the Florida Education Association and the lawsuit's lead plaintiff. It sends students to private schools that are "largely unregulated" and do not have to follow state academic standards, teacher-hiring requirements or accountability rules.

Backers of the tax-credit program, created by the Florida Legislature in 2001, include top Florida leaders, and many quickly decried the lawsuit, calling it "appalling," "disheartening" and "disappointing." They said the program provides an important option for parents whose children may be struggling in public school but cannot afford private school.

"Shame on them!" wrote Florida House Speaker Will Weatherford on Twitter. Former Gov. Jeb Bush called the lawsuit "the latest attack on parental choice by an entrenched education establishment."

The groups behind the lawsuit — the Florida PTA and the Florida School Boards Association among them — include some of those that successfully challenged the constitutionality of Florida's first school-voucher program.

In 2006, the Florida Supreme Court struck down the Opportunity Scholarship Program, the first statewide voucher program in the nation. The 20-page lawsuit filed Thursday in Leon Circuit Court cites the earlier case in arguing that the tax-credit program should be declared unconstitutional, too.

The impact of this new lawsuit could be more far-reaching, however. The first program was serving about 730 students when it was shut down. The tax-credit program should serve about 69,000 students this school year, or more than in the Seminole County school district.

Lake County parent Autumn Nelson said she applied for scholarships for her children because their local elementary school was struggling — it earned an F from the state this year — and seemed to focus solely on the subjects covered by state tests, with no time for art, music, P.E. or even recess.

Her three children are now thriving at Liberty Christian Prep in Tavares, which her family could not afford without the scholarships, she added.

When she heard about the lawsuit, Nelson said she thought, "Isn't it unconstitutional to accept my tax dollars and force my child to go to a school that I don't even get to choose and it's failing?"

The tax-credit program has been controversial since its inception. But opponents voiced more objections this year, when lawmakers increased the amount of the tuition voucher, from $4,880 to $5,272, and expanded the pool of eligible students. The teachers union, in a separate lawsuit filed this summer, contended the Legislature illegally approved that expansion.

That 2014 expansion represented a "tipping point" and convinced opponents to file the lawsuit 13 years after the program began, said Ron Meyer, an attorney for the plaintiffs.

Unlike the now-defunct program, the tax-credit program is not funded directly from the state budget. Instead, corporations donate money for scholarships and then get a credit on their state tax bill.

That program is "just a thinly veiled attempt to siphon taxpayer's dollars to private religious schools," said the Rev. Barry Lynn, executive director of Americans United for Separation of Church and State, which also joined the lawsuit.

But the tax-credit program should be more immune to legal challenges than the other voucher program because it doesn't take money from public education's budget — and its closure wouldn't necessarily mean more money from schools, said Daniel Woodring, a Tallahassee attorney who helped with the state's defense in the earlier case.

The U.S. Supreme Court upheld Arizona's similar tax-credit scholarship program in 2011, and the New Hampshire Supreme Court on Thursday upheld its state's program, Woodring added.

But Meyer said Florida's program violates provisions specific to Florida's constitution, so the other cases have no direct bearing.

The lawsuit says tax-credit scholarships violate the state constitution's requirement for a "uniform" system of "high quality" and "free public schools." And it argues the program violates the state constitution's prohibition against state money going "in aid … of any sectarian institution."

lpostal@tribune.com or 407-420-5273407-420-5273