Does nobody who says this remember their days in highschool?
Let’s say a bedtime of 9
School gets out at 3
Allot about 2 hours for homework, it’s now 5
Allot an hour for dinner, it’s 6
Congratulations! A kid has a whopping 3 hours of free time per weekday to enjoy the last few years of childhood. These are even relatively conservative numbers, HW could easily stretch into 3-4+ hours with an AP class or a particularly HW heavy teacher leaving a whole hour of free time! How wonderful.
Oops wait, a strict parent(s) now adds an additional hour for household chores, ah well so much for free time.