Well, to each his own on this one. No 2 people are going to see eye to eye with this. My high school band went and performed in Dublin's St. Patrick's Day parade, that was THE most awesome band experience EVER, anyway, we all had our chaperones. When I took my middle schoolers, yes MIDDLE SCHOOLERS to NYC to see Broadway shows, they all had chaperones, as one would expect.
Even on the high school trips, we were told that if you break the rules, you're out and paying to get home. Just because Disney allows 14 year old patrons to enter without an adult, doesn't mean that the 14 year old is capable of making adult decisions. That's up to PARENTING to decide that.
As I said, the norm for high school trips to Disney is that the kids have to be in a group and they can do as they please in the park for the day. Normally it takes an incident like this to ruin it for the next few trips, then they'll allow it again.
There is no chaperoning debate here because I've seen many adults that could use chaperones, and not kids.