As district leaders and union representatives sit down to negotiate teacher contracts, an invisible hand has already decided many of the potential issues for them. That's because states' collective bargaining laws set the ground rules for what can be negotiated. State legislatures generally take some areas off the table, such as teacher evaluation, transfers, and even teacher leave. Consequently, district leaders enjoy unilateral discretion in any of these areas.

The interplay of state law with local contract negotiation begs the question: do these attempts to limit what can be bargained really alter the end results? From the perspective of district superintendents, are these state laws the gifts that keep on giving?

Answering this question is one goal of The Collective Bargaining Agreement Project, a team of researchers led by Katharine Strunk of Michigan State University that has painstakingly collected and coded hundreds of agreements to shed some light on teacher contracts. Using these data, Strunk et al. studied how collective bargaining in three states—California, Washington, and Michigan—changed as the result of legislative reforms poised to limit the scope of negotiations, thereby shifting managerial decisions to district leaders.

Some clear tradeoffs emerged. While district leaders gained control in determining policies on the specific area removed from negotiation, unions felt emboldened to push for more concessions for other areas still on the table. Pass a law taking evaluation off the table and the result may be that unions become more aggressive on giving senior teachers more transfer rights.

Of the three states examined, only Michigan proved to be the exception for this dynamic. That's because that state had so aggressively limited across multiple areas what could be negotiated that the local unions had a hard time finding a viable issue to go to the mat over.

What's the lesson? Cherry picking a practice or policy to reform will likely mean tradeoffs.