Gem School

Gem School is a alluded location in Goiky. It is a educational institution for diamonds, according to Book.

History
In No More Snow!, Ruby was pressing buttons on Evil Leafy to escape her, and she pressed buttons that screwed up the process. After Ruby presses the yellow button, Pencil scoulds at ruby, and asks her if she went to gem school. Ruby says that she did not go to it, and Book mentions to Pencil that Gem School is for diamonds only.

Trivia

 * There is indeed a Recommended Character called Diamond, and one of Ruby's sisters is named Diamond, but it is unknown if they attend that school.
 * If Book is correct about the information that onky diamonds attend it, it is possible that there could be diamond clones across Goiky.