Abrien Sliver
I believe as a whole, Buddhism frowns upon cruelty to animals, but I think that dissection is condoned in that it is done in the pursuit of understanding
This and the fact that the animal(s) you dissect are most likely already dead. You aren't causing harm to anything.
Personally the question I would be asking is "How do I feel about it?" Are you ok with dissecting animals? Would you be if you received words of comfort? If it feels wrong, explain to your teacher your situation and see if you can find a compromise. If it doesn't feel wrong, go along with the class and try to get an A. What matters is what feels right or wrong to you. Follow your moral compass.