State House and Senate negotiators were unable Thursday to reach agreement on key details of a controversial proposal put forward by the teachers union to generate extra revenue for public schools through property taxes.

Senate Bills 686 and 683 stalled in conference committee and are dead for this legislative session.

The first bill sought to impose surcharges on investment properties and visitor accommodations to raise an estimated $500 million a year for public schools. The second bill contained a proposed constitutional amendment to ask voters whether the state should be allowed to tap into property taxes to fund education.

Different versions of the bills had passed out of both chambers and advanced to what’s known as conference committee, where negotiators for both sides work out differences. But Senate Education Chairwoman Michelle Kidani and newly appointed House Education Chairman Justin Woodson — the lead negotiators — were at odds over the bills.

“I’m just not sure what happened, because as we spoke about this throughout the hearings during this session, we kept passing it out of committees, and now we are here, at the last hour, and I’m finding that the support by the House has (waned) and the light is about to go out,” Kidani said during Thursday’s conference committee meeting.

She encouraged her House counterparts to at least advance the measure with the constitutional amendment, suggesting that lawmakers could continue to work on the enabling legislation and details of how the tax surcharges would be implemented.

“This constitutional amendment, at the end of the day, asks residents of Hawaii to decide for themselves if they want to invest in our keiki and fund our public schools through this surcharge,” she said. “Passing Senate Bill 683 and Senate Bill 686 is not the Legislature imposing a surcharge on a tax-weary public, but an opportunity for the public to decide for themselves.”

The fate of the bills seemed uncertain even before the measures landed in conference committee. Legislative leaders have raised concerns about potential legal challenges to the measures and appeared hesitant to approve a new tax when the Legislature is already considering an extension of the general excise tax surcharge on Oahu to bail out the city’s rail project.

“The House believes strongly that we need to do a better job at supporting our K-through-12 system,” Woodson said Thursday. “But at this point the House also does not conclude that this is the proper solution at this time.”

He called the legislation flawed, citing lingering legal concerns and disagreement over the threshold for property values that would be taxed and who should be exempted.

“It takes both chambers to vote for a particular proposal, and we do not agree that this bill, this proposal, is the right vehicle to move forward at this point,” he said.

Kidani disagreed and called the legal concerns irrelevant.

“Bringing up these ghosts serves only to distract from the true issue at hand,” she said. “We come across roadblocks every day in what we do. And in this case, if the courts want to challenge it, let them challenge it. But I think we should do our duty and protect the opportunity for educational funds for our keiki.”

Woodson suggested resuming talks next session.

“The House just feels that we want a strong foundation to move forward, so we would like to work with you next year on something that we can do in terms of increasing funding for our keiki,” he told a visibly frustrated Kidani.

Kidani said Senate negotiators at the meeting were prepared to vote to advance the bills.

“I want it for the record that the Senate was willing to be here, counted for, and to pass out this bill,” she said. “Unfortunately, the House did not agree, and the hopes for our keiki and funding for our education is dead.”

Corey Rosenlee, president of the Hawaii State Teachers Association, which had helped draft the measures and lobbied in support of the bills, expressed disappointment after the decision. He said the union’s internal polling showed two-thirds of voters would have supported the proposed constitutional amendment.

“The last two years have shown that legislators will not vote to increase funding for our schools, nor will they allow the public to vote,” Rosenlee said. “Our legislators must make education a priority. If they did not support the constitutional amendment, what are their solutions to our chronically underfunded public school system?

“Our keiki can’t wait any longer.”