Complex sentence: Seletar Institute (SI) was one of the four original centralised institutes (CI) in Singapore and one of the pre-university centres in Singapore that offers a three-year curriculum leading to the Singapore Cambridge (UCLES) General Certificate of Education Advanced Level examination.
Split into simpler sentences: Seletar Institute (SI) was one of the four original centralised institutes (CI) in Singapore. SI was one of the pre-university centres in Singapore that offers a three-year curriculum leading to the Singapore Cambridge (UCLES) General Certificate of Education Advanced Level examination.