Or, perhaps you could discuss the social contract, and how, in a school setting (among others), there are necessary restrictions to individual freedoms that arise from the need to prioritize the needs of the group. In this case, offering a wider menu of choices may not be in the best interest of the majority (having a lengthy discussion about this during instructional time certainly begins to impinge on the interests of the group).

...though I know that these discussions always have the potential of opening up even more cans...

...pronounced like the long vowel and first letter of the alphabet...