This is an interesting combination. I would use the zoo topic as an analogy for imprisoning the innocent for the spectacle and viewing of thers and depriving animals (people in our analogy) of living their lives to the fullest. Examples might be strip clubs where predatory men watch women dance topless or nude or the rings of prostitution or even child pornography. The death penalty can be tied in by mentioning the publicity that follows the death penalty through the media and by allowing executions to be viewed by private individuals and in some cases shown on television. An example here would be the execution of the Oklahoma City bomber which was televised. Teens going to college suggest that education produces an enlightenment that will not only guide them in pursuing their own interests in life but enlighten them to the dehumanizing effects of the death penalty and of trapping people into lives that serve other people's predatory and immoral needs.
As a guiding question, I would ask why people enjoy watching and participating in the misfortunes of others and how higher education can pull humanity out of this grasp. My thesis would be that focusing on educating oneself will reduce the need to participate in these behaviors and create a higher moral ground. I would reiterate this in the conclusion and draw a picture of a society without this level of immoral behavior.