TOPEKA — An economist tasked with reviewing a controversial public school funding study told lawmakers Thursday the "cutting edge" report meets his validity check.

He said student achievement can only improve by spending more but acknowledged there is no guarantee additional funds will help.

The assessment from Jesse Levin, of the American Institutes for Research, hardened anxiety for some lawmakers over the potential of a futile cash infusion. They face an April 30 deadline to deliver a plan to the Kansas Supreme Court that meets requirements for adequate and equitable funding.

A day after a House panel backed a plan to add $500 million over five years, Gov. Jeff Colyer urged lawmakers Thursday to pass a school finance bill by the end of next week and "stop the cycle of litigation."

"Any resources that are put in, we need to have outcomes and accountability afterward to make sure we're actually getting money into the classroom," Colyer said.

In a joint meeting, House and Senate lawmakers pressed for accountability after hearing Levin's praise for a study by consultant Lori Taylor. She concluded the state needs to increase spending by as much as $2 billion over the next five years to achieve student performance goals.

Levin identified concerns with Taylor's "scales of economy" index and decision not to lower funding for any district already receiving more than is warranted by her formula. But he said her conclusions were justified by comparing recommended funding levels to student performances. Districts that stand to benefit from more spending, he said, are the ones that struggle with student achievement.

"If you want to meet the thresholds that are in place," Levin said, "you can’t do it without spending more."

Rep. Clay Aurand, a Republican farmer from Belleville, presented Levin with a metaphor involving fertilizer and crop yields. At some point, Aurand said, he can put more fertilizer in the field without improving the results. Levin told him economists learn about the law of diminishing returns on the first day of Econ 101.

"There are no guarantees that more spending will directly result in achievement," Levin said.

Reflecting on the recurring recommendations of studies conducted over the past two decades, Rep. Melissa Rooker, R-Fairway, said "we need to invest more resources."

Wednesday saw the first movement on a spending increase when Rep. Steven Johnson, R-Assaria, proposed adding $500 million over five years. The House K-12 Education Budget Committee endorsed the plan as a show of progress. Colyer said the total, which is lower than the $600 million proposed by former Gov. Sam Brownback, is "a good discussion point."

"I think, right now, it looks pretty positive," Colyer said. "We need to let the legislative process go forward."

Ongoing efforts to relieve lawmakers of their responsibility to fund schools led to introduction Thursday of a proposal to change the Kansas Constitution. The amendment in a House committee would declare the power to appropriate funding for education belongs exclusively to the Legislature and isn't subject to judicial review.

Earlier in the week, Sen. Steve Fitzgerald, R-Leavenworth, tried to secure funding to place such an amendment on the November ballot but failed to find enough votes on the Senate floor.

Sen. Molly Baumgardner, R-Louisburg, touted the work being done in the Senate throughout the session at the committee level.

"Our goal is to continue to find strategic opportunities in funding to help the schools help the kids be more successful," Baumgardner said.

Lawmakers will return from the Easter holiday with one week of work remaining before a scheduled three-week break.