Well with all things pointing toward a 5pm launch time on Friday, you'll stand a better chance of getting hold of one rather than it launching in the morning while you're at school.
No doubt about it, it's going to be busy. As with other Apple product launches, people just seem to go nuts. You have people like us from these forums queueing, the people who don't come on here but still love Apple products, and people who see the queues ask what its about and decide to join the queue because they'd love one.
Personally, if I were you, I'd be up at midnight/1am/2am on Friday morning for when hopefully the online orders will open and check the delivery lead times. If I knew I couldn't get down to the store early, or if I knew I'd arrive late (as you will be due to school) I wouldn't expect to get my hands on one in retail stores due to the obvious forthcoming shortages. People still seem to think they'll have plenty of stock later that day, or over the first few days after launch, but when it comes to it there's always shortages.