I was in high school when the principal made the announcement over the speaker system.
This is the theory I believe the most.
Oswald shot JFK in cahoots with the mafia and paid for through Fidel Castro.
Why? Because Castro had stopped several attempts of JFK using the CIA trying to kill Castro. Castro had asked JFK to stop trying to kill him, but JFK continued and Castro was in fear for his life.
The mafia hit in Dallas would have had to be approved by Carlos Marcello of New Orleans, as Dallas was in his territory. Carlos Marcello's mob boss was Tropecante of Florida. Tropecante was the only mafia casino hotel owner in Havana to get his funds released after JFK's death. Castro's government had nationalized all of the American casinos in Cuba after the 1959 commie revolution.
The American deep state hid this from the American people because the people would have wanted war against Castro. The problem with that is a year before in 1962 when America backed Russia down in front of the whole world, it was America had to promise the Soviets that America would never again attack Castro's Cuba. Thus the cover up.
