Three anti-tax groups slammed a proposed ballot initiative raising money for schools Wednesday by arguing that the measure would lead to billions in higher residential property taxes.

Spokesmen for the proposition's supporters, which include movie director Rob Reiner and the California Teachers Association, said the critics were willfully distorting the issue.

"They're just trying to scare homeowners," said Jim Farrell, a spokesman for the initiative campaign. "This doesn't affect residential property owners, and they know that."

Although the secretary of state's office has not yet certified the measure, it appears headed for the November ballot under the title "Funding for K-12 Education and Voluntary Preschool Program."

By raising taxes 55 percent on commercial and rental properties, the initiative would generate an estimated $6 billion annually for preschools, K-12 schools and teacher salaries.

The measure states explicitly in a section on "purpose and intent" that it doesn't seek to "increase or in any way affect the property taxes paid by homeowners on non-commercial property."

A December analysis by the nonpartisan Legislative Analyst's Office reached the same conclusion.

But at a Sacramento press conference Wednesday, Jon Coupal of the Howard Jarvis Taxpayers Association and two other anti-tax activists said a drafting error in the measure would make residential properties also subject to some $3.5 billion in higher taxes.

"We are not talking about a clerical error or some minor oversight," Coupal said. "What the tax experts at the California Taxpayers Association have identified and what we have identified through our own legal analysis is a huge error that could cost taxpayers billions of dollars."

Coupal and the other anti-tax activists said residential property could be included because the initiative isn't clear on whether to assess the land residential dwellings are built on.

In one paragraph, the measure says a second home "and the land on which that dwelling is constructed" are exempt from any changes in the initiative. An earlier paragraph, however, for principal dwelling units, doesn't include wording about land.

"Accordingly," the anti-tax groups' analysis says, "that land could be subject to a 55 percent annual tax increase."

Coupal acknowledged the clear language in the intent section of the initiative, but he said he's worried that a judge could see the rest of the measure as requiring residential property tax hikes.

"As we all know in California, how a judge interprets constitutional language is never a sure thing," Coupal said. "If we run up against a strict-constructionist judge who looks at the plain language of the Constitution, then I think homeowners are at a real risk of seeing the land underneath their homes increase."

Robin Johansen, a lawyer for the campaign who helped work on the initiative, said Coupal's argument was "a non-issue."

"It's so clear what the intent is, which is not to raise residential property taxes on homeowners," she said. "A lot of people looked at this and worked on it and there is no way a judge would ever make that ruling."