This is the 5803rd most frequent Japanese word.
はじまっ
"はじまっ" is a conjugated form meaning "to begin" or "to start."
The term 'はじまります' is used here to indicate the starting time of the school, representing the concept of beginning or initiation.
学校は8時に始まります。
The school starts at 8 o'clock.
Here, '始まった' is used to signify the commencement of the game, expressed in the past tense to indicate the action has already begun.
試合がついに始まった。
The game finally started.
In this sentence, '始まる' conveys the planned initiation of a new project, emphasizing the future aspect of the beginning.