Why can't I go to school without any worries and without my heart racing when I'm completely aware that there is no reason for be like this?

Hi there. I understand you feel overwhelmed for no reason, School is the place where you have to take tests, deliver presentations and other activities that give you a specific grade for your performance. You might feel that you yourself/your parents/your teachers have certain expectations towards your performance. You know what matters the most? That you give the best you can. You will feel satisfied and your heart will not race if you take that perspective. No one really is perfect and guess what: everyone feels anxious at times. Choosing to handle this by doing the best you can is how you can fight the anxiety.

School can be a very nerve-wracking thing. There is a lot of stress (even if you are not aware of it). There is homework, tests, interacting with peers, etc. There is so much that can be making you nervous without you even realizing it. This is perfectly normal. When you feel yourself getting like this, take a moment and take a few slow deep breaths.

Somehow you may be feeling anxious because you put so much pressure on yourself or someone else does and it makes you anxious

That's a sign of anxiety. That means your brain is constantly nervous and paranoid of something bad happening. Or you might have some kind of phobia to be in public. Either way, you should seek some help, from yourself, from your friends, or from a therapist. Remind yourself that everything is going to be fine, take deep breaths and take some breaks if you feel like it.