Photographers: how much should an amateur charge for a shoot?

I'm currently in a photography 101 class using a Nikon N55 film camera.

For one of my assignments, I needed a model, so I advertised around asking for volunteers. I got an overwhelming amount of people who were interested in helping with the project, and a few who asked if they could get copies of the photos from the shoot.

Since I'm buying my own paper and film, and I'm spending hours in the darkroom printing them myself (it's not like I'm dropping them off at a photo center or something quick and convenient) what would a good price be to charge them for the photos? Since I'm not a professional, I don't know where to begin. Prices, anyone?

Added (1). Hmm, maybe I should've clarified a bit. I would give them a free copy of the photo I'm using for my assignment for them to take home, but what I'm wondering is if they request that I take additional photos for them to keep. Maybe after my assignment is over and they like how the photos look, they would want me to take more for them. Should I charge the cost of paper and film or is charging anything still a bad idea since I'm not a professional?

Added (2). Basically, it seems from what I've gathered is that these people are looking for some good, quality pictures of themselves to take home. I'd be willing to go beyond my class assignment to take extras for them, but as you all know, the cost of materials isn't exactly cheap.

Student work should be free or not be sold. You're there to learn, and what you've learned is worth far more than the material you've used (hopefully). Give them the photos. They'll be more likely to say good things about you to their friends and you'll get more jobs that way, paying ones. Even then, us photographers really don't charge that much. Charge an hourly rate for taking the pictures… Say… Twice the minimum wage. Then add the charge for materials.

First of all, get the person you finally decide to use to sign a model release. As far as making extra prints for them goes, you might want to check with your teacher. Under normal circumstances you are the copyright owner of the photos you shoot. But, in some cases when you are shooting for an employer or under someone's tutelage, I believe it is them who hold the copyright and final say on what can be done with them.

Normally photographers pay models, not the other way around.

Either work in trade, or pay your model around $100/hour.

Nothing.
If you charge for your work, you're a professional -- that's the definition.
If you are an amateur, you don't.

In the situation you mention, you don't charge anything for the photos. You're trading the photos for the model's time modeling. It's called "TFP" (trade for prints, or in the digital age, TFCD). Your model will be spending hours modeling for you, and signing a release (DO get a release signed!) for you to use their image -- your hours in the darkroom and the money you spend on materials for their prints are your payment to them for modeling.

The key thing you said is that you are an amateur which means that people should not be paying you to take their pictures. It is fair and reasonable to charge them enough to cover your expenses but not profit. You will be ready to make profit soon enough. If you want to set up paid shoots and people are willing to pay you, then you just need to come up with an amount that they are willing to pay. Not too much to start either, just be glad you have people that want you to shoot them.