Everyone in school thinks I am bitter. How can I change their minds?

Well first thing you need to find out is why? If you really want to change their minds you need to find out why they think you are bitter in the first place which is why you ask them, once they tell you why or maybe they don’t (which is okay too) you can find out more and then try to do your best to stop acting like that and maybe their opinion will change. If not then they aren’t worth your time.

I'm my experience, and based on it, i believe that it's a two factor thing. First of all we cannot change other people's minds, second, the only thing we cam change is our attitude towards us and them. So if people think you're bitter, maybe try changing the way you act towards them, being kind, compassionate, careing. But always keeping in mind that it may not help at all, because we cant change what people's thoughts. And in that case, there's only one way to fix it: don't take things personally.

don't worry about changing anyone's mind, be yourself, love yourself, be confident in what you do, and after all that they'll see who you really are which is a strong caring person.

Prove them wrong by not being afraid how showing them your emotions and by taking kind and compassion little gestures.

Just be yourself and eventually they’ll realise how great of a person you are, don’t listen to those guys, they need to get their own lives instead of making other people’s feel worse than theirs.

By being kind to them, helping them whenever needed but if they still don't then uhh too don't waste your time proving it.

Start being more friendly maybe help someone with something they will soon realise your kindness.

By being a big ray of sunshine spreading positive vibes everywhere you go, not letting anything get you down.

Simply smiling more, and having a softer expression showing the majority of the time can normally help. If you go out of your way to be nicer, people will eventually (maybe not immediately) understand that you’re not a bitter person.

think about your mannerisms in a day that lead to people thinking that, write them down, and work on fixing them one at a time