Sound body, sound mind has long been the accepted wisdom.
But schools have traditionally promoted brains and brawn separately.
Not so at Naperville Central High School west of Chicago. Here the kids who struggle with math and reading go to gym class first.
"What we're trying to do here is jump start their brain," says Paul Zientarski, chairman of the Physical Education Department at Naperville.
So the very first class of the day is physical education.
And at Naperville, exercise isn't confined to the gym. There are bikes and balls right in the classroom. Even in reading class, these kids are constantly on the move.
Scientists say Naperville is on to something.
"Exercise, good fitness-based exercise, makes our brain more ready to learn," says John Ratey of the Harvard Medical School.
At the University of Illinois, Dr Charles Hillman's research shows that after a 30-minute stint on the treadmill, students actually do up to 10 percent better at provlem solving.
"It's good for attention, it's good for how fast individuals process information, and how they perform on cognitive tasks," says Hillman.
At Naperville, the test results are astounding.
Reading scores up nearly twice as much. Math scores up by a factor of 20.
In an era when many schools are cutting PE programs to save money, Naperville is looking for new activities to get kids moving.
This isn't your old-fashioned gym class, where the teacher is wearing a whistle acting like a drill sergeant. These kids are learning to square dance. And every one of them is getting a workout.
The scientists say this sort of exercise is an ideal brain-builder: aerobic activity gets the heart rate up. Complicated movement stimulates thinking.
"All their brain cells are working," says Ratey, "And when their brain cells work, they pour out neuro transmitters, they also pour out these brain growth factors which help our brain cells knit together."
Sophomore Caitlyn Porcaro used to get C's and D's. Now she gets A's and B's. She says the exercise helps her focus.
"It kind of gets the gears in your head turning...It makes you actually think about what you're doing. Instead of, oh, this is math class. I'm going to zone out."
In fact, at Naperville, whenever the math teacher senses his students are zoning out, he gives them a "brain break," a short burst of physical activity.
For the students, the benefits seem to add up fast.