GRAND RAPIDS, Mich. – StudentsFirst.org’s political action committee has donated $500,000 to the campaign against the union-backed Proposal 2, with the organization’s leaders saying they want to preserve school reforms.

The proposal, also called Protect Our Jobs and Protect Working Families, would enshrine collective bargaining in the state constitution, invalidating existing or future state or local laws that limit the ability to join unions.

Critics, including Attorney General Bill Schuette, said about 170 state laws would be affected.

StudentsFirst, an advocacy group based in Sacramento, Calif, “strongly supports collective bargaining for teachers,” but supports some of the limits on what unions could negotiate.

“Proposal 2 would keep bad teachers in the classroom and turn back the clock on key education reforms at a time when Michigan schools and students need our help the most,” said Andy Solon, the organization’s Michigan state director.

“Putting students first should be priority one for every parent, teacher and school administrator, but this ballot measure puts the needs of adults above those of children and in one fell swoop will eliminate the most important schools reforms we’ve put in place in a generation.”

RELATED: Michigan Decides 2012: Proposal 2 would put collective bargaining in Constitution; does it belong there?

StudentsFirst lobbied lawmakers to pass a series of reforms including changes to teacher tenure, eliminating policies where the newest hired were the first laid off and annual educator evaluations based in part on student performance.

The group was founded by former Washington, D.C., Chancellor Michelle Rhee, who testified before an overflow crowd in the Michigan Capitol in March 2011, urging lawmakers to support the reforms.

“I love teachers – effective teachers,” she told a smaller group of lawmakers and educators that day. “No one has a harder job than an inner-city teacher. There is nothing more noble than working as a teacher.

“But if you raise some of these issues you are labeled 'anti-teacher' or a 'union-buster.' I'm not a union buster. But teachers have a very effective organization lobbying on their behalf. I want to be effective representing the other side, out children.”

The $500,000 donation went to Citizens Protecting Michigan’s Constitution, which is supported by business and community organizations, as well as school groups including the Michigan Association of School Boards and the Michigan Association of School Administrators.

Proposal 2 is supported by a coalition of unions and Democrats that collected more than $8 million, according to a July campaign finance report. And updated report is due this week.

Supporters have said the proposal will give teachers more of a say in their working conditions and preserve local control of education.

"When teachers have a voice on the job, it improves the quality of education," said Sara Wallenfang, a spokeswoman for Protect Working Families.

"But corporate special interests are actively trying to turn our schools into profit centers. StudentsFirst.org is paying several hundred thousand dollars to silence teachers because they expect a return on that investment, which will come at the expense of our kids."

Email Dave Murray at dmurray@mlive.com and follow him on Twitter @ReporterDMurray or on Facebook.