We don't have synonyms for school bell yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are school meal.
(N) :
The ringing of a school bell (In foreign) announces important times to a school's students and staff, such as marking the beginnings and ends of the school day, class periods, and breaks.
(N) :
The ringing of a school bell (In foreign) announces important times to a school's students and staff, such as marking the beginnings and ends of the school day, class periods, and breaks.