School Shoes
From Inkipedia, the Splatoon wiki
The School Shoes are shoes in Splatoon. It is 2-star rarity obtained through the Inkling Girl amiibo.
Its ability is Ink Saver (Sub) which decreases amount of ink consumed by your Sub weapon.
Unlock
Complete these 4 missions the amiibo gives you to unlock it:
13 Shifting Splatforms — Midnight Rendezvous —
14 Octoling Assault — Skirmish at the Skatepark —
15 Undeniable Flying Object — Bluefin Sighting —
Boss 3 Roll with the Punches... The Rampaging Octowhirl!
Appearance
Like the School Uniform, the appearance of the shoes changes depending on your inkling's gender. The shoes come with long socks if worn by a female, and none for male inklings.
Abilities
The Power Boots come with the Ink Saver (Main) ability as a main ability.