Hello, Aimee! I actually had a very similar experience. I was quite outgoing in elementary school. After transferring to a new school, I became more reserved. Being reserved made me somewhat of a target for bullies, which led to my becoming even more reserved. By the time I reached middle school, I was barely talking to anyone, and I couldn't look people in the eyes. Fortunately, I found a great group of friends in high school, and once I felt comfortable around them, I began to open up. I think I will always be an introvert, but I have come a long way in overcoming my fears/anxiety about social situations.

There are some things that are within your control, and it's important to recognize those things. For example, it sounds like you would be more confident in class if you took the time to study. I know that may sound harsh, but it makes sense that you would be afraid of replying to teachers when you are uncertain of what to say. If you take the time to study, then you will be more competent, and subsequently gain more confidence in your abilities. In the meantime, it might help to speak with your teachers after class and explain what's going on. You're not the first anxious or shy student they've had, so they should be understanding of your situation. They may offer some tips for dealing with the situation, or they may say what I said about studying more in order to improve your competence and confidence.

With regard to your friends (and your friends' friends), it might help to ask yourself what goes through your mind when you're around them. Are you afraid of how you'll be perceived? Of what they will say or do? You have had some of these friends for a long time, and they have been accepting of you up until now... so what makes you think they would suddenly reject you because of something you say or do? The worst thing you can do is let the anxiety or "shyness" get the best of you, because failing to interact with friends can lead them to believe that you're "cold" or "stuck up." If telling them how you feel is too difficult, then you might want to consider writing a short note saying that you're nervous and need some encouragement from them when you're having a hard time speaking up. Seeing as how they used to be in your position, I'm sure they will be understanding and have ideas for how you can begin to overcome these feelings!