any school not allowing the use of something you are going to be using while you are in the work force is nuts and putting you behind the curve. sure you can do it all out by hand, but if you tried to do that in the real world your project manager would kick your ass to the curb for not knowing how to use it.

honestly, how can they expect you to work productively in the business sector if you have to sit down and do out every integral for just a rough estimate?

:Edit:

they banned them at my high school after they noticed that I was getting all A's on the tests but not doing well with anything else...
they gave me an 83 and i still got A's, it just forced me to be there an extra 15 minutes over what i used to. these schools think that just because you are using a tool you don't know how to actually do the material, which is not always the case. THIS ISN'T CHEATING, you still need to know how to do it.