Charter schools have generated support from politicians in both major American political parties, while stimulating intense debate among interest groups. We investigate whether and how public attitudes come to mirror interest group polarization or politician consensus in order to understand what drives public attitudes as policy debates mature and citizens learn information that drives advocates to opposite sides. Using survey experiments, we assess how views change in response to policy cues. Mirroring debates among advocates, we assess whether the role of private companies and non-union teachers polarize opinion. We find that the public responds to cues linked to unions and polarizes based on liberal and conservative ideology as well as attitudes toward unions. This helps to explain how ideological polarization can grow even in the absence of strong partisan sorting among top political leaders. The report includes a bibliography.