What a great age to start stuff! The mind is ripe, the self confidence is way better! I think that we grow so much and that aging should be seen as a treasure as we all know how our mind worked in our teens lol.
Mean stuff teachers said almost always stick because we are so young and we have no awareness of our potential and own value. So we tend to believe what others say. I also had some teachers like these. I congratulate you for overcoming that. Your story reminds me of Steve Harvey. the TV guy. He had a serious stuttering problem and one of his teachers laughed and mocked him for wanting to become a TV anchor. Now that he is a millionaire and successful he confessed that he sends a TV every year to that particular teacher to allow her to watch him on TV every time. Hahaha imagine the suffering of that teacher's ego. She deserved it for mocking a child's dream. Who knows where that teacher is now, but that mocked child is now a millionaire. So from that story and yours I learn that we should always follow our dreams no matter what the naysayers say.