Why would it be appropriate for the two chaperones to upgrade themselves into a separate business class cabin, thereby leaving the kids unsupervised?
ADDED: It also seems bad that AC kicked off the two chaperones but let the kids fly alone. The news story seems to imply that the two chaperones were on the same PNR (IIRC it said same ticket, which can't be right as the two adult women obviously cannot share a seat) but the kids booked in a way that they either weren't linked or the airline agents ignored the situation. Why wasn't everyone booked as a group? That might have discouraged booting the two adults as AC would then need to rebook the entire group together, which could have been difficult. Also, why didn't the chaperones object to being separated from their charges?