Nothing at all

I'm rather busy with school right now. Everything's going fine but I'm usually very tired after a school day, and though I can't call it bullying people are starting to act strangely when I'm around... mainly my class mates. They become nervous, perhaps even afraid, when I appear. They're not mean and I don't find their behaviour offending, nor do I mind being alone (I'm not very close to any of my class mates), I actually like it. What's troubling me is why they do this. I do have my theories but it still seems weird that they would change their behaviour so suddenly.