There's a huge difference between "most clocks" and "most clocks I've seen" - especially if your clock experience is restricted to schools.

Do you see a lot of schools? Do you know whether the schools you've been to all use the same supplier? How broad is your school clock experience? How many clocks do you think you've seen, ever?

Most clocks I've seen recently (I can recall exactly 1) have seconds hands. Regardless though I'm not suggesting "most clocks" have seconds hands...I'm just making a quip about how traditional, analogue, clocks have seconds hands to deal with the exact problems noted.