Enrolling a child in a Singapore school as a foreigner
Families arriving mid-year are doing this against a start date, which is what makes the paperwork urgent rather than merely tedious. The translation part is small, but it sits at the front of the queue.
The birth certificate does the heavy lifting
It is read to establish who the parents are, and it is the document asked for in almost every case. Where the original records parentage differently from a Singapore certificate, the fields are translated as they stand rather than mapped onto a local equivalent, because the school is entitled to see what the original actually says.
Records from the previous school
Reports, transfer letters and year certificates are used to decide placement. Translated as a set and kept in order, they let someone make that decision in one sitting. Translated piecemeal, they invite a request for the missing year.
Grades are rendered with their original scale rather than converted into a local equivalent. Conversion is the school's job, and one done for them tends to be distrusted.
If the school has not told you what it needs
Ask, because requirements differ between schools and between local and international systems. If you are against a deadline and cannot wait for an answer, the birth certificate is the safe one to start with.