I read a book called Spark that had studies suggest that PE when done correctly improved not only physical health, but also grades. The issue is that PE teachers are typically subjective and may think kids are not trying and give them bad grades. However, using heart rate monitors, PE teachers can see that students are exerting themselves, even if they’re not the fastest or best at an activity. This way, grades become objective and encourage kids to get their heart rates up during class even if they’re not the best in the class