Why does "old-school" mean "old-fashioned"? Is there any historical reason?
"Old-school" is just another way to say "old-fashioned." There isn't any particular historical reason, but it is connected to the idea of being a traditionalist who prefers doing things based on how they were in the past - hence, "old school." You can use "new school" in the same manner, but it is less common. Ex. He belongs to the old school of traditional baking. He hates using machines and prefers to do everything by hand.