At the end of an emotional meeting Tuesday night, the Osseo Public School Board voted 4-2 to revise its policy on how books in school libraries are chosen and challenged. The revised policy lists procedures under which residents of the school district — as well as students, parents or guardians — can raise concerns about library materials. Opponents call the measure a pathway to banning books — one that goes around a new state law widely referred to as a “ban on book bans.” Earlier this year, the Minnesota legislature passed a law blocking public schools from banning books because of the viewpoints or messages they contain. This debate is a recent example of the heightened political atmosphere hanging over libraries and school boards around the country. “It’s certainly front of mind for all of us,” Edina elementary school librarian Ashley Krohn said. She spoke with MPR News host Cathy Wurzer from Rochester, where she and other librarians from across the state gathered Thursday for the Minnesota Library Association’s annual conference. Krohn is the group’s intellectual freedom chair.