Practical and relevant solutions won at the close of this year's Senoko Sustainability Challenge, including ways to amplify sunlight in classrooms and incentivise hotel guests to save energy.

For several months since last November, more than 400 students had put themselves in policymakers' shoes to come up with ways for Singapore to stay resilient against the impacts of global climate change.

The winners' ideas were "practical and doable", said biologist and former chairman of the National Parks Board Leo Tan, one of the judges.

"That was the most important thing. They were not dreaming (about) science fiction ... they were saying: we can do this today," he said at Wednesday's awards ceremony at the Mandarin Orchard hotel.

A team from NUS High School of Mathematics and Science topped the secondary school category by brightening their classrooms using just sunlight and a system of mirrors and prisms.

They had observed how classrooms remained fairly dim during the day even with windows open.

With sunlight penetrating further in, this could reduce the need for ceiling lights during the day, said team member Lim Yi Fei, 17.

Minister for Education Heng Swee Keat told students at the ceremony that they would "grow up to be the leaders and decision-makers of tomorrow".

With this responsibility, they have to be aware that their small 'green' efforts over time would have a large impact, he added.

This year's challenge, first launched in 2005, attracted more than 100 entries from 52 schools.