In a renovated warehouse in a weary-looking section of troy, n.y., 25-year-old katie bellucci has the rapt attention of 27 fifth graders. They are singing, stamping, clapping and waving their hands in the air—far more excitement than you would expect for ratios and fractions. The class is working together on a word problem involving a fictional basketball team with a win-to-loss ratio of 9:3. What is the ratio of losses to total games played? Bellucci gets everyone involved in breaking down the process (“What do we need to do first?”). Once the class arrives at a fraction—wins plus losses, divided by losses, or (9 + 3)/3—she encourages them to reduce it. “Okay, who's got the GCF?” she says, referring to the greatest common factor. She zips up and down the aisles, cajoling one student and then another for one more piece of the solution. The students track her every move, knowing she may call on them even if their hands are down. “I'm seeing so many lightbulbs and so much diligence,” she says. If an answer comes easily, she will push ahead with that student and ask for the how and why behind it. The bell rings, and as the kids file out for lunch, each one hands Bellucci an “Exit Ticket”—the solution to two problems that exemplify the core lesson of the day, which Bellucci will scrutinize to determine if the class mastered the day's objective.