Non-PRO English Art/Literary General / Conversation / Greetings / Letters

"Just the previous night, George had been over for dinner
and had started asking my father questions about his time in
high school. That my father had ever been to high school was
funny, and that he was willing to talk about it? Shocking. Somehow,
with George there, asking, lightly, the tight box of Dadness
was open for looking. I was the lead in my high- school play, Dad
said, sipping his water. I dropped my fork on the floor. What?
Oh sure, Dad said. Everyone did it, he said. A musical? George
asked. Of course, Dad said. Even Mom laughed. Dad filled his
mouth with yam. What musical? I asked, and we all waited
while he went through the process of chewing, and swallowing,
and dabbing with his napkin, ending in the new word 'Brigadoon'".

this is from an american novel. dad's play must have taken place around the seventies or eighties, in the states.
i'm rather confused about the nature of this play: is it something that graduating students perform annually? do all classes do it on a regular basis? is it done once a year...? additionally, the "everyone did it" part confuses me as well. i take it to be the lead part, so how does everyone do it? or am i totally lost?