The results of Packham’s paper on the Fitness Now program support the basic takeaway that the design of P.E. courses is what’s most consequential, and they hint at two interconnected factors that experts suggest tend to undermine the impact of such curricula. For one, P.E. programs often rely on a superficial notion of gym class—conceiving of physical activity as little more than a timed run around the track, for example, or a game of kickball—and this results in worse offerings. And then, when students feel forced to take these basic offerings, they may resent the classes more than they would otherwise. “Older kids have already formed these important eating and exercising habits, and changing their daily decisions is more complicated than just providing money for jump ropes,” Packham says.

Despite greater recognition of the academic benefits of physical activities—including guidelines from agencies such as the Centers for Disease Control and Prevention stressing that kids should get at least an hour of such activities a day—schools began to deprioritize P.E. about two decades ago, and the cuts have persisted in many cases , suggests Kohl. Accompanying this shift has been a movement away from casual activities such as recess, which experts argue is one of the more effective means of promoting children’s physical health. An immense body of research demonstrates the positive benefits of increased recess time, which schools started to cut after No Child Left Behind was signed into law, because of the policy’s emphasis on academic subjects such as reading and math.

Justin Cahill, a veteran P.E. educator who’s taught at an Atlanta-area private school for the past decade or so, stresses that it’s the typical application of physical education rather than the fundamental concept that results in bad outcomes. Until the past few years, P.E. classes tended to focus on kids’ acquisition of skills, such as dribbling a ball, and the fulfillment of universal benchmarks, such as the ability to run around a track three times within some specific amount of time. This approach, he says, “breeds stagnation and disinterest—the kids are like, ‘Yeah, this is ridiculous.’” It can also, as Packham’s study suggests, breed resentment: After all, in this “old school” version of P.E., certain kids are bound to struggle.

Read: Why kids need recess

Cahill maintains that many P.E. programs are high caliber, successful in both engaging students and producing positive health and wellness outcomes. Echoing the findings outlined in Kohl’s book, he says that positive results are contingent on a multifaceted and holistic design—what he defines as programs that inspire children to exercise without realizing they’re exercising, that simply ensure they’re constantly moving, during recess, frequent “brain breaks” to get out “the sillies,” morning jogs, and, yes, regular P.E. class. Positive results are also contingent on experienced, empathetic P.E. teachers—those who know to modify a curriculum to meet a certain student’s needs, and to give kudos to that child who can’t run around the track. After all, research shows that people can get a good workout even when walking, and the more important thing is to create a healthy relationship with exercise that can last for decades.