Marble goes to a boarding school with her sisters. The only issue is,that when your mute like her,it's hard to ace classes.
She can't answer questions but she does all the test right. It is up too Limestone,Maud,and Pinkie to help Marble.
But soon a fellow student reveals Chrystal Ponies are in deep trouble and Marble must save a pink Pegasus called Cadence,the future princess.