Her O-level grades were good enough for her to earn a place at a junior college or a popular diploma programme at a polytechnic.

But instead of taking the conventional routes like most of her peers after receiving her O-level results two years ago, 18-year-old Celine Low pursued an 18-month diploma in management studies at SIM Global Education (SIM GE), a private institution here.

Ms Low, who graduated with the diploma last September and is now pursuing a business degree from RMIT University through SIM GE, said the shorter time to finish her studies was a draw.

With module exemptions from her diploma programme, she is on track to finish her degree in 2018, two years ahead of many of her peers. "I knew what my interests were. I wanted to learn about marketing and managing a business," said Ms Low.

While the costs of studying at a private school are higher, "I think choosing the private route was the right decision for me", she said.

Other students choosing to pursue further education at a private institution after the O levels cite similar reasons, including the variety of higher education options and the shorter time it takes to claim a diploma or a degree.

Major private institutions here said their enrolment of O-level holders has been steady over the last few years. An SIM GE spokesman said its foundation studies and diploma programmes see an annual intake of more than 500 O-level holders. Currently, the private institution offers two foundation studies and four diploma programmes, in areas such as accounting and international business.

PSB Academy said O-level student enrolment for its diploma courses, which typically takes between 12 and 24 months to complete, is "fairly consistent" every year. Last year, it had an intake of about 1,000 O-level holders. It offers 11 diploma programmes in areas such as retail management and industrial engineering.

Some private institutions, such as Kaplan Singapore, have even introduced new diplomas. Kaplan, which has more than 25 diploma programmes across eight disciplines such as law, introduced two new diplomas - in property management and Web technologies - last year. It takes an O-level holder about 10 months to complete a diploma at the school.

Besides attracting students looking to complete their studies in a shorter time, private schools also provide a route to further education for those who did not fare well at the O levels.

Mr P. Danush's grades did not qualify him for a place at a junior college or a preferred polytechnic course. After his O levels, the 19-year-old took up a four-month professional certificate in business management, followed by an eight-month diploma in tourism, hospitality and events management at the Management Development Institute of Singapore (MDIS).

Mr Danush, who is now studying for an advanced diploma in tourism, hospitality and events management at MDIS, said the private institution has given him a chance to pursue his interest.

"I've always wanted to be part of the tourism sector," he said. "So I am glad that I have a chance to pursue this passion."