CN recommended from the City Journal:
Teachers like smaller classes, and understandably so. The advantages include fewer papers to grade, students to manage, and parents to deal with. The teachers’ unions like smaller classes, too. Smaller classes mean more teachers—and more union dues. And parents like smaller classes because they believe that their children benefit from more individual attention. Everyone agrees that smaller classes are better, right?
In a word: no. Much of the rhetoric supporting small classes is demagogic and runs afoul of the research.