Maybe it’s just me, but there was something special about having graduation IN the school where I had spent my entire life as a teenager. Having a city ‘general assembly’ just doesn’t get it. Where is that ‘final goodby?’
Most schools don’t have an indoor space big enough for all the graduates and guests.
My graduation was in the school football stadium, and there was no limit on attendance. In later years, it was decided that outdoor graduation was too hot (or rainy), and they started holding them in the city convention center. This required issuing limited numbers of tickets to each graduate for his family/guests.
There is that and each school has it’s own tradition. Apparently the bagpipes are played at one of these schools ceremonies and will be squeezed in with pieces from other ceremonies.
At my school we graduated at the church across the street. However, we got dressed and lined up in the school and there was a procession from the school to the church. It’s a BIG DEAL still today to participate in “the walk.”