The No Ball is the official ball for The School for Evil, which is also an Evil version of Snow Ball. The first No Ball was held in the first trilogy of SGE, orchestrated by Sophie herself as part of her master plan.
The No Ball was created without any rules. This was stated in the very first No Ball, except that they need to win the Circus of Talents, or the No Ball will not be held. Instead, the Snow Ball will.
The No Ball was created by Sophie in her first year, after the Circus of Talents was held. This was a rage to show the staffs and Evers that they want to have their own ball too, and thought this is unfair.