I have a presentation today at school, and I'm really anxious?

Before you start your presentation breathe deep in through your nose and out,through your mouth, be mindful of your breathing, it effects us a lot. place your hand on your tummy and feel how it fills with air, and then let the air out again. slowly, maybe also close your eyes while doing that. repeat this for 5-6 times, and dont stress about it. also massaging your earlobes for a couple minutes helps realxing your nerves.

And remember, what is the worst that can happen? You are prepared and you will rock this, this is your presentation!

lots of love xx

Make sure you know the concept of your presentation. Ask yourself what is about to be presented? Once you think you got this, practice presenting in the mirror and try not to think about how others will think of you once you finished presenting. I know that you probably presented your presentation, but for the future, practice reading your presentation in front a friend or family member, someone who you know will give you good feedback on how well you did, that person should also be someone you are comfortable with. Also, when you are about to present, you should take a deep breath and present with confidence by reminding yourself how hard you worked for that presentation, and if you ever have a group presentation, then you wouldn't really have a problem there because your group member(s) is/are here to support you and motivate you. Again knowing what you have to say really does help when you are presenting and it will make everyone else think that you do know what you're talking about, which will want to make them listen more as further explain.
I hope you did well on that presentation of yours, and if not, then you shouldn't worry about it for too long because there is always next time. Practice makes accuracy and closer to success. Just keep trying, be a go getter.
Sorry for babbling too much. But, I really hoped this helped and got through to some people! Good luck to anyone who is presenting! :)