Graduation
Typically graduation symbolizes accomplishment, but it can also be seen as absolute participation in an organization's program. So in this case, graduation is a complex symbol, because do these characters really want to lend that kind of credence to this institution? From the last book in this series, we know that this Commonwealth school is extremely immoral in its policies. They realize that they are about to become part of the conspiracy they most resent.
The anti-school
Higher education is a symbol in literature for self-improvement, and for many, it also represents the transition from childhood and childhood responsibilities to adulthood with its adult responsibilities. In this case, the school is a symbol for that same responsibility, but because the school is known by these characters to be evil in its design and intention, the transfer to their adult responsibilities might mean fighting against the system that educates them.
The Testing
The Testing returns in this installment of the series as a symbol for judgment. The Testing has a name that might remind the reader of the standardized testing that often happens in school, so perhaps the Testing is a symbol for the dehumanizing aspect of state-imposed education standards. In Graduation Day, the Testing represents the final threshold where the individuals are tested by the government, but instead of losing opportunities, the failing students lose their life.
The planted rebellion
The rebellion used to represent hope for change, but the last book discovered that the rebellion is planted. This means that in Graduation Day if they want to end the Testing, they can't use the rebellion as their method. They must partner with President Collindar instead. This whole dilemma is symbolic. It symbolizes the need to collaborate with existing power structures for real change. They feel they are compromising their movement, but when the Testing is finally brought to an end, the anarchist rebellion is shown to be less effective than collaboration with others.
Unintentional chaos
The symbolic consequence of doing the right thing is that the kids manage to disrupt the status quo. In the aftermath, they are surprised by the unintentional results. They have brought a great deal of chaos into their community, even though they believe their change was good. This just goes to show: Doing the right thing doesn't mean everything will be easy and pretty. Sometimes the right path is one that takes time to adjust to. They must endure in their beliefs to see the full benefit of the changes they helped to bring.
