Trying to find this answer and not having much success.
My daughter has a school trip to Europe, booked through a tour operator, which ended up being booked on BA for most of the itinerary (IAD-LHR-FCO). This is a group of 50-60 travelers and now that the trip is close she has realized that travel expert dad has not meticulously planned things like seat assignments because it’s a school group tour

and she wants to sit with her friends. Not having a PNR to even look up is killing me but I digress…
This got me wondering how seats are assigned. I’ve never done a tour operator booking and have no idea. How would BA allocate seats on a A380 to 50+ kids and their chaperones? Allocate a few rows and just go alphabetical?