Don't worry about what people think of you - the good ones will know that T1 doesn't make any difference! It might feel weird testing and injecting in front of other people, but I guarantee most of them won't even notice, and if they do they'll probably be too polite to ask you about it. If some mean people do bother you about it, just ignore it and stick with your friends. And then log on here and come and rant about it with us - we love a good rant!
Lots of people don't understand T1 very well and may have misconceptions - they might ask you if you ate too many sweets or drank too much soft drink, they might say you can't be diabetic since you're not fat, they may think that some miracle diet will cure your diabetes. Don't listen to them - if they are open minded you can use it as a chance to educate them, if they are not then you know the truth, so don't let them persuade you otherwise!
Make sure you talk to your teachers - tell them that you are a T1, you need to test/eat/inject sometimes in class, and what to do in an emergency.
