Accused of cheating but innocent

During a test, I looked up at the clock to see how much time I had left. The clock is not directly in my line of sight, so I moved my head. My paranoid teacher then accused me of cheating. I could potentially be in a lot of trouble now. I’m a hard-working A student with good test scores and lots of ECs/leadership. First of all, any ideas how I could defend myself? It’s essentially her word versus mine, and I have a feeling that school administration would side with a teacher over a student. Also, in the event that I am found guilty of something I didn’t do, how would this affect my chances of getting into selective schools?

I’m really stressed out now. Any advice would be appreciated.