Filed under: FitnessPhoto: WittFitt, LLC Less students are slouching in their desks these days, they're sitting attentively upon colorful exercise balls. While many kids report trading a chair for a cushy ball is fun, classroom-designed ball chairs are really about improving learning, reports the Chicago Tribune. Perching atop a ball chair requires kids to constantly engage their core muscles, which is simultaneously turning on their pre-frontal cortex for better mental engagement and less impul