Sounds good. As a science teacher, I do see some problems (what grade, by the way?). First, we like to see repeated trials. In other words, it would be better to have several snakes on rats and several snakes on mice. Secondly, make sure she eliminates all other variables (i.e. Same sex, exact same temps, exact same accomidations, exact same water, same feeding schedule, etc.) - be sure to document this (judges will be impressed by the strict adherence to the scientific method). Make sure she records and logs the mass of the prey items as well. This would be an important step to make sure any results you see are in fact due to the different type of food and not amount of food.
As far as potential problems go...what if one snake, as BPs are so famous for, stops eating...she'll all of a sudden have a project with no real data to collect.
Thats about all I have to say at this point. I'm sure I've forgotten something. Feel free to e-mail me if you have any questions! Good luck!
Joe Pociask Pythons