I use a Toshiba Satellite A505. It's amazing and has a 12 Cell battery. So I have battery life for potentially 8 hours, depending on what I am doing. The only down side is that it is a bit heavy, but it really isn't a problem at all. I totally think it would be worth your while to look into it.
As stated in other forms I would check with the instructors at the college I know at my college they let me use a computer because I have a learning disability with reading and writing, you know the most common unerdiagnosed dyslexia, I have had it so long I have learned to adpt but still always double checked my self but defiantly check most instructors will be ok with it as long as you are not recording anything with it as some one else posted you might want to try an iPad with a blue tooth key board... To mention it I am on an iPad now, my first Mac electronic device so far loving wish I had it in school. I hope this helps if you have any questions about maybe what kind of questions to ask about the computer to your teacher about how they want you to use it I can help