School sizes do change over long time horizons as demographics grow. This is true.
But school buildings have limited capacity and teacher:student ratios should be maintained. These cannot be changed instantly. Planning happens according to people actually living there, so if a lot of people are circumventing the rules and cheating their way in it breaks the system.
> School sizes do change over long time horizons
Not even very long horizons. For example, a hot housing market can cause a rush of young families into a district as older retirees cash out and move to Florida or whatever. Schools adapt to this.
I agree following rules is important. What kind of example are you setting for your kids, right? But having some perspective is also important.