Thank you for the opportunity to help you with your question!
The theme of the story is that self confidence can help one to achieve anything one wants. In this story, Angie was unable to learn her times tables simply due to lack of self confidence, though in a moment of crisis she displayed her inner strength.
The message conveyed to readers is that keeping one's confidence high can help one to sail through difficult situations. Bullying and negative factors can also be overcome by believing in oneself. Also, in a crisis, it is helpful to keep calm and try to keep the others calm so that the crisis can be overcome.
Please let me know if you need any clarification. I'm always happy to answer your questions.