On the UD seats 62A/K and 63B/J are exit row seats as they face in to the mid cabin emergency exits. The criteria for sitting in those seats for landing and take off is quite clear on ba.com:
You have selected a seat in an emergency exit row. In the unlikely event of an evacuation this passenger will be expected to assist in the opening of the emergency door.
Therefore, they must:
- be over the age of 12 years
- be able bodied and fit enough to open and operate an emergency exit door
- be able to understand instructions given in English
- not be substantially deaf or blind
- not be pregnant
Our airport staff will verify that each passenger meets the exit row seating requirements or they will be moved to an alternative seat.
The supervisor should not have overidden the requirement. At any stage (check in, gate, onboard) if someone spopts your son's agen he will be moved at least for landing and take off. I guess the obvious solution is put him in any other seat on the UD, only those four out of the 20 up there are exit row seats.
You have mentioned 63K though and that is not marked as an exit row - just done some dummy bookings, so I am a bit confused about why that didn't work for your son if that's where you were seating him?
EDIT: I wonder whether the problem was more to do with this issue rather than exit row seats?
To get the best choice of seats, it’s best to reserve your seats in advance, for which you might have to pay.
If you don’t choose your seats in advance, we’ll do our best to seat your family together a few days before your flight departs, from the limited selection of seats available. This might result in your family being split over different rows or across the aisle, however we will make sure each child under 12 is seated with an adult from your booking. Anyone over 12 years is treated as an adult in our system, so we may seat them separately.