There have been many unintended consequences with this.
Lines are substantially longer, even to the point where people commented that if they had known that Grad Nite was being handled this way this year, they would have come a week or two earlier. We had to go to
Disneyland on Weds. to renew our annual passes and we ate Dinner at PCH Grill and I overheard several families mentioning this. Apparently, the lines were getting really bad at most attractions, I overheard something about 80+ minutes for Jungle Cruise. I honestly don't know if that was an exaggeration or not, as we never went into the parks that day.
We went a couple weeks back after work to meet up with some friends and the park was empty, of course they were having computer problems that day, so there is some debate as to why it was as empty as it was, but overall it was dead.
The Toy Story lot has the last bus leaving EXACTLY at park closing and if you aren't on it, you have to walk, even if you were in line for the shuttle from what we were told.
The lines for the parking structure trams were substantially longer than normal, due in part to the fact above and in part to the fact that all Gradnite parking was placed there.
There were more security checkpoints open, but there were being a lot more thorough with their searches.
Now, you might question why Disneyland would make this change, I have to admit that I loved my Grad Nite, but I can understand the need to change it.
By doing this, they can limit what is open after 10:00 to one side of the park, meaning fewer CMs. They end up not needing to spend as much in overtime. Security isn't as much of an issue, I heard last year it took some buses as long as 3 hours to get the OK to let their students off the buss, as they were searching the buses individually. This way, the students go through the security checks the same way that everyone else does. I would also imagine that they may have even said, we are not allowing anyone in after 10:00 PM.
As for the chaperons, I have never understood the need to chaperon students once they have graduated High School. I would make it clear that they are on their own and if they break any laws or get into other trouble, the school will not defend them in anyway. In addition, they would be responsible for their own transportation.