What Causes Aggressive Behaviour And Temper Tantrums In A Child?

Hi my name is marquette I am asking bout things my daughter is doing. She has been acting out in school. She has thrown things bit the teacher spit in her face. All while smiling and happy. She doesn t throw a fit or mad when she is doing it. She is just doing it. It has to progressed home now to where she will not listen. I have sat her down and try to ask and explain. She says ok and she won t again but as soon as ur done talking she s back to doing it all over. She is 5 gonna be 6 in Oct. I m just concerned cause some brought up about pandas and pans. I have looked into it and she has all the signs of pandas. Is there any way to to find out for sure if she does or if she is just acting out. Thank u for ur time.