The first thing to try: Tell Yahoo to forward your email to your school address. I assume you are given a school email and are allowed to check that.Next, you might install Portable Firefox on a flash drive at home, then bring that to browse the web from. If your administrator is paranoid, though, there are two possible ways to stop you: blocking Yahoo where your school connects to the Internet and preventing unknown programs from running. If your admin did the former and not the latter, see my suggestion here.You may also be able to reboot the computer with a Linux LiveCD in the drive, connect to the Internet, and browse from that. Two possible problems: if booting requires a password, or if connecting to the school's network does.Please note my general warnings to the "How to get around your school blocker" person. If you do any of the above preparations at home, make sure your parents are watching; explain what you are doing and why.