You might want to go to Dell online and get a laptop through them directly if the model the school offers is less than acceptable. Unless they are offering a Dell too. But then, it could be the Vista that is the problem. You could get one through the school with Vista and then wipe it and install XP. Just sayin'.
It seems that the Dell Latitude that the school is pushing is getting less than favorable reviews and some people in the reviews have been asking Dell to go back to the D series, which is what you have I think. Which would explain the difference. :)