Gov. Scott Walker’s collective-bargaining reforms have saved Wisconsin from becoming a fiscal basket case like Illinois, and a new study suggests they are improving student learning too.

The Governor’s biggest achievement in eight years in office has been curbing the power of government unions by limiting collective bargaining to wages and requiring public employees to contribute more to their pensions and health care. Superintendents could also attract better teachers by paying for performance.

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Mary Bell, president of the Wisconsin Education Association Council teachers union, declared at the time that Mr. Walker “has taken an ax to our public schools” and that the reforms would result in “the destruction of public service and public education in this state.” But public schools and student performance are better now because of the reforms, according to a new study by the Wisconsin Institute for Law and Liberty.

The study examined state math scores before and after the reforms were implemented. Reading scores weren’t considered because the state changed language arts tests after the reforms took effect. Math proficiency increased by an average of 2.1% across school districts after districts implemented the reforms. Improvements were found in the state’s small town, rural and suburban districts, but curiously scores in urban schools didn’t budge.

One reason may be that administrators in Madison and Milwaukee resisted the reforms and may not have taken advantage of their new powers. This theory is supported by a study last year by Yale economist Barbara Biasi that found high quality teachers—that is, those who improved student learning most—tended to move to districts where teachers could negotiate their pay while poor performing teachers stuck to regimented salaries.

State Superintendent Tony Evers, the Democratic candidate for Governor against Mr. Walker, has pledged to roll back Mr. Walker’s collective-bargaining reforms and end a voucher program that helps 28,000 low-income students attend private school in Milwaukee. He also wants to raise taxes on the wealthy, manufacturers and farmers to juice spending for public schools no matter their performance.

Mr. Walker’s reforms have saved the state billions of dollars and reduced property taxes. If Democrats take control of the statehouse in November, they’ll attempt to reverse this progress and give unions the run of Madison again.