Our health is, in the end, more important than any other basic item in our lives. Being unhealthy decreases productivity, quality of life, and satisfaction with things in general. A prime example of this comes from a natural experiment in English schools: districts where schools participated in a program to provide "health, fitness, and social skills" training improved more quickly
on academic measures than did non=participating districts.
Without more details, I immediately wonder if the participating schools weren't also participating in other efforts, or making other simultaneous changes, which might skew the result. But even in that case, it's clear that healthier kids make better students.