noun
opening ceremony (school term)
Refers to the formal ceremony held at the start of each school term in Japanese schools, typically involving speeches and announcements.
始業式で校長先生が新学期の目標について話した。
At the opening ceremony, the principal talked about goals for the new term.
明日は始業式だから、早く寝なきゃ。
Tomorrow is the opening ceremony, so I have to go to bed early.
入学式 is the entrance ceremony for new students entering a school, whereas 始業式 is for all students at the start of a term.
Compound of 始業 (shigyō, 'start of work/school') + 式 (shiki, 'ceremony'). The term is a standard modern Japanese school-related word.