Eris' story at school is pretty different from everypony thought. Discord was really afraid the other children would make fun of her or even harm her. Of course if that'd ever happened he would make sure they will regret it. Celestia kept saying that he was over reacting and she was sure the other ponies would love her little baby.
When she arrived to school, everypony looked at her confused, her huge ears, her eyes, her paws, everything with her was a bit… off. But they actually apporached to her and tried to be her friends. That only made her feel weird and unconfortable. Even when she looked weird, it seems that she didn't look wierd enough. Her first day in school was strange, everypony asking about herself, trying to show her Canterlot School, trying to be her friend… It seems Celestia talked about the new member to the other mothers and they turned a bit… crazy… They really wanted their children to be "the princess' best friend" and so they could take advantage of that. They definitely convinced their children to be Eris' best friend in school.
Eris can't remember their faces actually, they seemed more like shadows without faces to her. After her first day, Eris managed to convinve Celestia to "never ever go to school ever again". Fortunately she didn't have to convince Discord, and so he managed to find a good tutoress for her, Flurry Heart, who will teach her everything.