I have been through exactly this when I was 13, that is now 21 years ago! I can remember it so clearly and I only told my parents but nothing was done. I think they thought I was overreacting (I did and still do have a tendancy to lol) It was in maths for me, I never understood the subject really and was very shy so certainly never put my hand up to answer. She knew this and would pick me out of the whole class to answer something I couldn't. I would sit there in silence going redder and redder, she would glare at me and the whole class would stare. It was awful and I actually sat there crying once but didn't have the confidence to do anything about it. God typing this is bringing it all back! Looking back now I think she was an absolute cow who obviously had issues herself and clearly got a kick out of humiliating me. Like others have said, you don't have to take this. I would give it a chance first though before saying anything, she might have changed if you're lucky. If she does get up to her old tricks again then definitely speak to one of your favourite teachers about it and ask him/her for advice. Good luck and I hope it all works out for you.