How the hell did a high school graduated become a goddess, along with her sister?

I don't think that divinity requires higher education. Or any education, for that matter.

Farming is learned on the farm.

You just can't let Shizuha have one moment of spotlight, can you, Minoriko?

No one has even realized that if Shizuha has barely finished high school and doesn't know about moe and stuff, how does her little sister?