All schools that follow the national syllabus operate a January to December calendar. The school year is broken into three terms with 3-4 week breaks in April, August and December. School exams are mostly biannual now with exams in June and November.
For those taking the GCE Ordinary Level exams, those are held in December followed by around a 6-month break before the commencement of Advanced Level coursework. The Advanced Level exams are held in August of each year.
International schools following international syllabi such Edexcel, Cambridge or IB start around late August and end around June. They have shorter 2-3 week breaks in December and April and of course a longer “summer” break from June to August.