With a veto Thursday of a proposal to upend schoolteacher layoff rules, Gov. Mark Dayton wiped out one of state Republicans' top priorities.

Dayton said the measure was an example of "prejudice against public school teachers" that singled out hard-working teachers by negating long-establishing bargaining rights, replacing them "with only vaguely formulated ideas."

The veto heightens the tension between the DFL governor and the Republican-dominated Legislature.

The education measure would have ended the "last-in, first-out" seniority-based system of layoffs that governs Minnesota public school teachers whose local contracts do not already allow consideration of other issues such as teacher effectiveness.

"The governor has dealt a major blow to teachers, schools, students and parents across the state," said the proposal's chief sponsor, Rep. Branden Petersen, R-Andover. Petersen and other supporters met with Dayton repeatedly to urge him to sign the bill.

Petersen issued what he called a "public apology" for Dayton's veto. "I am sorry that Governor Dayton chose to side with big-labor special interests and sell out our children's futures," he said.

The measure moved through the Legislature with almost no DFL support.

According to Petersen, the bill got the votes of one DFLer in the House and one in the Senate.

The issue inspired heavy lobbying inside and outside the Capitol. It raised the ire of union groups, particularly the powerful Education Minnesota teachers union, which spent $500,000 lobbying last year.

"Instead of tackling the serious challenges facing public education, the Republican majority's top priority for our schools this session has been to further regulate teacher layoffs. The priority should have been making layoffs unnecessary," Education Minnesota President Tom Dooher said.

Julie Blaha, president of the Anoka-Hennepin teachers union, said teachers she speaks with are more worried about class sizes and the welfare of their students during tough economic times.

"Ultimately, this is not the biggest issue facing our schools right now," Blaha said of the legislation. "I would rather the focus had been on looking at fair funding."

Bill supporter Vallay Varro, executive director of the Minnesota Campaign for Achievement Now (MinnCAN), said she expected the veto.

"You always hold out hope that [Dayton's] going to do the right thing at the end of the day, considering what research is saying about keeping the best teachers in the classroom and considering what Minnesotans have been saying," she said. "Unfortunately, it didn't shake out that way."

MinnCAN spent $260,000 on lobbying last year.

The measure was also one of the state Chamber of Commerce's top education priorities. It spent more than $2 million lobbying last year.

In his veto, Dayton said that the Republicans were trying to move too quickly on changes, without allowing new teacher evaluation systems to be developed. He said that after those systems are completed, in 2015 or 2016, it would be appropriate for the Legislature to decide how to incorporate them into layoff decisions.

That wasn't good enough for supporters of the vetoed bill.

"We shouldn't be waiting around to embrace common-sense reforms to improve our schools," said Tim Melton, vice president of legislative affairs for the overhaul-supporting organization StudentsFirst.

Staff writer Eric Roper contributed to this report. Rachel E. Stassen-Berger • Twitter: @rachelsb