MADISON, Wis. — University of Wisconsin System regents unanimously approved a plan Friday to raise in-state undergraduate tuition for the 2018-19 school year if Republicans lift their tuition freeze.

The proposal calls for keeping tuition flat for 2017-18 and raising it by no more than the rate of inflation for 2018-19.

It didn’t detail how the rate of inflation would be calculated, but System President Ray Cross told the regents Friday at their meeting at UW-Eau Claire that system officials would use the latest annual average at the moment it sets tuition for that year. The annual average is currently 1.1 percent; raising tuition by that much would generate about $7.5 million, system spokeswoman Stephanie Marquis said.

“The adjustment is modest,” Regent Gerald Whitburn said. “It should be affordable for students and for their families. And it is in fact required as we look at system and campus financials.”

The tuition freeze has proven popular among parents and students, including James Langnes, a UW-Whitewater business major who serves as a student representative on the regents board. But he acknowledged that students will have to pay more at some point.

“Tuition can’t remain flat forever,” he said.

The plan hinges on whether and when Gov. Scott Walker and Republican lawmakers lift the freeze that’s been in place for four straight years. That move came after the GOP learned in 2013 that the system was sitting on massive reserves while raising tuition annually.

The prolonged freeze — coupled with a $250 million cut Republican lawmakers imposed on the system in the last state budget — has led to layoffs and fewer class sections, increasing time to graduation and student expenses in the long run, system officials say. Walker has said he wants to continue the freeze for another year as he prepares his 2017-19 state budget but hasn’t committed to extending it for a sixth year.

The plan states that tuition is a key factor in college affordability but a high-quality education can be delivered in a timely manner only if tuition keeps pace with the cost of living.

“The bottom line is simple,” regents President Regina Millner said. “Continued budget cuts and frozen tuition cannot be sustained.”

The regents also provided material with the plan showing they’ve asked Walker to increase financial aid by $19.2 million in the next state budget, and that system officials are working to find administrative cost-savings. Such costs represented 6.2 percent of its budget in fiscal year 2014 compared with the 8.8 percent national average for colleges.

Annual resident tuition at UW-Madison, the system’s flagship school, is $9,273. UW-Milwaukee charges $8,091 for tuition. The system’s other four-year schools’ rates range from $7,361 at UW-Eau Claire to $6,298 at UW-Green Bay and UW-Parkside. UW-Stout’s tuition is $234, but that school also charges per credit. Students at all the schools pay hundreds of dollars in fees every year as well.

Asked about the system’s plan, Walker spokesman Tom Evenson said only that the governor is continually reviewing how to make education more affordable and appreciates that UW officials support a freeze for 2017-18. Staff members for the co-chairs of the Legislature’s budget-writing committee, Rep. John Nygren and Sen. Alberta Darling, didn’t respond to messages seeking comment.

Jason Klein, a spokesman for the Associated Students of Madison, UW-Madison’s student government arm, said in an email that tuition is too high but the regents are hamstrung by dwindling state aid. He said tying increases in state funding for the system to the rate of inflation makes more sense than raising tuition.

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