The heated battle over a controversial school tax credit bill is about to sizzle as opposing groups square off today in dueling State House rallies.

Organizers expect thousands of students and their parents to descend on Columbia to voice opinions about Gov. Mark Sanford’s tuition tax credit bill, which would give tax breaks to families who send their children to private school or another public school.

Today’s rallies, which will be attended by advocates for both private and public schools, are underscored by the increasingly ugly tone of the debate surrounding the bill.

Sanford will keynote the supporters’ rally with a speech from the State House steps.

One constituency that will be heavily represented on both sides is home schoolers, who also would qualify for tax credits under the plan, dubbed Put Parents in Charge by its supporters.

The families of some 14,000 home-schooled children in South Carolina are split on the bill because some fear it would invite increased state regulation.

Ann Ashley, director of New Beginnings Home School Association in Summerville, and other home-school families fought to gain autonomy from state regulations in the mid-1990s. Any erosion of that freedom is unacceptable, she said.

“By accepting money, it allows the state to come into our homes to determine what we can and can’t teach,” Ashley said.

Kathleen Carper, president of the South Carolina Association of Independent Home Schools, said Ashley and other opponents of the bill are “misinformed.”

Carper, whose group represents 1,200 families from around the state, said the bill is crafted so it wouldn’t intrude on what parents teach.

On curriculum matters, home-school families now answer to one of three entities — local public school boards, Carper’s home-school group or “third-option” groups.

Third-option groups were created in 1996 and are made up of 50 or more home-school families who operate independent of state oversight.

Members of those groups are leading the anti-tax credit faction among home schoolers.

Groups from all over the country have poured hundreds of thousands of dollars into the fight, which is expected to be a national test case for those who favor public school alternatives.

The furor over the bill is unusual because it’s taking place in what would normally be a post-election-year lull.

State Superintendent of Education Inez Tenenbaum last week blasted one group, South Carolinians for Responsible Government, for running radio ads she says are unfair to educators and children.

Tenenbaum and others believe the bill would siphon money from already cash-strapped public schools.

Denver Merrill, spokesman for South Carolinians for Responsible Government, said his group is simply pointing out problems with the state’s public education system.

“It’s not our intention to make this ugly,” Merrill said. “Any time you have a campaign on an issue, differences of opinion are going to come out.”

A billboard looming outside Merrill’s Gervais Street office illustrates the point:

One side is a plea by the S.C. Education Association to support public schools; the other side is a pitch for the tax credit bill.

The emotionally charged nature of the debate is not lost on home-school circles. Carper accused anti-tax credit groups of using the Internet to mislead people about what the bill would do.

“That kind of thing hurts the whole home-school community,” said Carper, adding that the focus needs to be on alternatives to public schools.

The larger issue, she said, is to expand options to parents whose children are stuck in failing or unsafe public schools.

“We live in a free society, and parents shouldn’t be forced to send their children to one school,” Carper said. “When it comes to K-12 education, there’s no choice except for people who have a lot of money.”

Reach Stensland at (803) 771-8358 or jstensland@thestate.com.