AUSTIN — Two fellow Republicans on the State Board of Education are hammering Texas Land Commissioner George P. Bush over a claim in a campaign mailer that his office contributed $4 billion to public schools during his tenure.

In an open letter published Wednesday, State Board of Education members David Bradley of the Beaumont area and Tom Maynard of Williamson County in Central Texas blasted Bush and accused him of trying to claim credit for funding public schools over the last few years when their board has put up most of that money.

"For the current 2018-2019 biennium, you and the GLO [General Land Office] have agreed to contribute $300 million — nowhere near the $4 billion you claim to have contributed in your campaign piece," the letter reads. "How can you in good conscience, take credit for the $4 billion provided for Texas students by the State Board of Education?"

"To say the least, we are deeply disappointed by your misleading, inaccurate campaign representations," the letter continues. "Texas students, teachers, parents and taxpayers deserve better."

Bush's team characterized the letter as a "laughable attack" from political opponents and defended the mailer, saying it refers to the revenue the land office has generated for the Permanent School Fund over Bush's tenure: $4.39 billion. The General Land Office generates money for the fund by negotiating and managing leases of mineral rights on millions of acres of state-owned lands.

Brittany Eck, a spokeswoman for the agency, said growing that fund is a "direct benefit to public education" and that Bush was able to generate "impressive revenue gains" despite the lowest average oil prices in about a decade.

Moreover, Eck said, the metric is the same one used by former land commissioner Jerry Patterson to tout the office's success when it generated a then-record $1.2 billion during the oil boom in the 2014 fiscal year. Under Bush, the agency has generated more than $1 billion every year, including a record $2 billion in 2017.

Bush, the nephew of former Texas Gov. George W. Bush and son of former Florida Gov. Jeb Bush, is now locked in a fierce re-election campaign with Patterson and four other opponents. He has been mired in controversies of late, with opponents criticizing his handling of the Alamo and Hurricane Harvey recovery, as well as political donations to his campaign from businesses who won contracts from his office.

Miguel Suazo, a Democratic challenger, harped on the controversies in a prepared statement.

"Another week, another controversy - do we really want a guy who has so many self-made disasters to be in charge of helping us fend off natural disasters?" Suazo said. "Maybe we should send Bush some help because the guy is in way over his head."

Bradley told The Dallas Morning News that Eck's explanation was "disingenuous" and that he'd sent the land office the letter before publishing it but had not received a response. The land office denies that. Eck said she first learned about the letter when it was released to news outlets Wednesday.

"They'll provide you with receipts on what the GLO took in, but that's only the half of the checkbook that shows deposits," Bradley said. "That's not money that went into public education."

Bradley said the only way to quantify how much money the agency contributed to public education is to add up how much it distributed to the Available School Fund, which pays out money to fund Texas schools. Otherwise, he said, the money is just sitting around in investments.

Patterson, Bush's main primary opponent, also criticized the campaign mailer, saying "money doesn't go to public schools until it's sent to the Available School Fund."

"Generating income for the Permanent School Fund is one thing, paying income to the Available School Fund is quite another," he said. "If they don't understand the distinction, we've got really big problems."

Since his tenure began, Bradley said, Bush's land office has only committed to distributing $300 million to the Available School Fund and made no distributions to it during the 2016-2017 biennium — his first in office.

That has forced the State Board of Education to make more distributions, Bradley said, because it is required by the Texas Constitution to determine a payout from the Permanent School Fund to the Available School Fund before every legislative session. Those calculations take into account the combined assets of the board and the land office, though the land office has not been required to pay from its coffers for more than a decade.

The education board doled out $2.11 billion to the Available School Fund during the 2016-2017 biennium and plans to distribute $2.47 billion during the 2018-2019 biennium, the letter said. Those contributions add up to $4.58 billion from the board in that four-year period.

"It's like if you had to pay your neighbor's revenue taxes," Bradley said.

Eck said distributing money to that fund is not the only way to contribute to public education in the state. As chairman of the three-person School Land Board, Eck said, Bush voted for and approved a move to distribute $490 million over the next biennium to the State Board of Education.

And by growing the Permanent School Fund, Bush has kept up other benefits the fund provides, like guaranteeing bonds issued to Texas school districts with lower credit ratings.

"Commissioner Bush, in his tenure has done more to increase and contribute to the [Permanent School Fund] despite lower [oil] prices," Eck said. "He has consistently worked to benefit public education by generating revenue to the [Permanent School Fund]."

Bradley remained unconvinced.

"That's your job — to collect the rent. That's what they're doing," he said. "What they haven't done is they haven't distributed it."