Criminal offence

Please would love some feedback how to deal with a situation that happened at school today. My daughter is 13 and is undiagnosed and waiting her assessment. I'm beginning to have issues with her not going to class but today I was in for total shock. So today first I had message stating my daughter was not in class to calls from the school police man stating my daughter had a knife and was flashing it about. I'm angry upset and at my whits end this is very out of character and now she is getting charged. She is a good kid and how do I punish her. My partner is arguing with me saying she blaming everyone other than herself. We spoke and she says she doesn't know why. She gets bullied for being different. She has been in her room since lunch no Xbox or phone.apparantly it's not a good enough punishment. I need help and thought on this. Thanks

Ayrshire