While the declining birth rate has led to fewer full-time students at the five polytechnics during the day, the campuses are a hub of activity at night, thanks to adult learners.
The number of training places that were filled by these older students grew from 42,000 in 2012 to 77,000 last year, according to figures from the Ministry of Education (MOE). A participant can take more than one course.
An MOE spokesman said: "The expected decline in cohort sizes frees up resources for the post-secondary education institutions to ramp up their efforts in other ways, while at the same time working closely with external partners to meet industry demands."
In 2015, the latest year for which such figures are available, 24,251 full-time students entered the polytechnics, compared with more than 26,000 in 2012.
Cohort sizes are projected to fall between 10 per cent and 15 per cent by 2025. Although the polys would still have a critical mass of students, they are paying closer attention to the adult learning space.
They have relooked their offerings to make them more relevant to the jobs and skills needed in today's economy, said poly officials.
The polytechnics are also ramping up courses in in-demand areas such as data science, business intelligence and cyber security.
In total, some 1,800 courses catered to working adults were offered across the five polys last year, compared with about 1,000 in 2012.
These programmes - which include the Earn and Learn courses, specialist and advanced diplomas, and shorter modules - are funded by MOE and SkillsFuture Singapore.
Mr Albert Toh, director of Republic Polytechnic's (RP) Academy of Continuing Education, said: "From focusing primarily on pre-employment education, we're moving to a mix of pre-employment and continuing education and training. Beyond full qualifications like a diploma or a degree, the call today is for workers to upskill, or learn a second skill."
Mr Suresh Punjabi, director of the Professional and Adult Continuing Education Academy at Singapore Polytechnic (SP), said some 1,500 students attend night classes every week.
One of them is Madam Annie Ng, who went for evening classes at SP twice a week for a year. She completed the specialist diploma in Web development technology in April.
The 49-year-old sales administrator in a company that manufactures satellite communication equipment wanted to learn IT-related skills. "If I wanted to switch industries, the Internet, information technology is the way to go," said Madam Ng, who hopes to take up courses in areas such as data analytics and cyber security next year.
In the last two years, the polys have even started to customise training for firms looking to upgrade their workers' skills or help them learn new skills. For instance, RP has been conducting short courses on drones since 2015 for government agencies and firms in the construction business. "It's not just about flying drones. Organisations are now looking at using drones to inspect buildings and superstructures like cranes and oil rigs," said Mr Toh.
Another example is a short course on social media, which RP started this year. Said Mr Toh: "More companies are using social media to drive their marketing and outreach, and older people are learning to use such platforms as a new skill. We cannot afford not to study... because you will find yourself lacking and left behind."