While one can debate the needs of people to eat meat (which I don't want to do here), one can argue that there is little value in allowing a 7th grader to cut open an animal to learn. Most people will not be going into science or medicine, and therefore I think that most of that can be done with a sophisticated model. Veterinary dissections are different (as they are serving a direct purpose in educating future doctors).
When we eat animals (wheter or not you believe in that), we are fulfilling a biological need. The food pyramid and all that jazz. But killing of an animal for learning purposes, one can argue, does not fill a biological need and can therefore not be compared in the safe way. I totally respect your opinion, though! To each his own.