I think people are trying to jump me at school? What should I do?

For a couple of weeks I've been working really hard and saving all the money I could get to buy an iPhone 4… Well, lately in my Physical Education class, these three black guys have been asking me about my phone (What plan are you on, where'd you get it, how many gb, what's your number, let me see it, unlock it for me and show me your password, etc.) and I havn't really thought nothing of it, until today one of them pulled me away while I was dressing out. I had my iPhone sitting on the bench and one of them put his arm around me being friendly, telling me that he needed to ask me an important question, and he tried to lead me to the bathroom, but I told him to hold on a sec and I grabbed my phone. He asked me if I wanted to buy some weed and I told him no, then I walked away. Then later on my friend came up to me and told me they've been watching me and he thinks they are trying to jump me and steal my phone, and that they would have taken it from me if he didn't follow behind us to the bathroom. I'm really worried now. What should I do besides call the police and tell the teachers? I don't want to be a snitch, and I have some friends that will back me up if they tried to jump me, but I really don't want to fight. What should I do?

Stop taking the phone to school? Why would you even bring an iphone around black people in the first place?