Day dreaming??

There was a stage where she cries everyday when we bring her to school. It is like separation anxiety starts all over again. She just cries when she reaches school but after some persuasion she is alright and enjoys herself in class. We do not know what happened in school and been playing the guessing game with her.
We even asked the teachers but they did not think that there is anything wrong with her in school. We thought that she might be bullied and does not know how to explain to us. But teachers did not realize anything, the girl just like to be the ‘big sister’ in class. We all think that it’s the after school thingy, cos things only happened when she is out of school on the way to the school bus. Although it’s a very short distance, she is upset by the girl’s actions. So we told her that it alright and just keep her distance from her but I guess she is still upset.
The next thing, teacher told us that she day dreams in class! We are all so shocked and started to think of all ways to talk her out but the suitation did not improved. After much discussion with my sister (who is a childcare educator), we realized that she might be bored with the things that the teacher is teaching. She might be looking for something more challenging and excited. We interpreted that she might be thinking that, hey I already know this, why teacher keep repeating. So we had a talk with the principle and told her to expose more things to Sherry. So she moved her to a higher class and now she is very happy to go to school. She no longer cries but sometimes she is still bothered with the girl.
Anyhow, we just want her to go to school happily.