They picked up 50kg of trash along the banks of Lower Seletar Reservoir, as part of an awareness programme organised by the North West Community Development Council and Waterways Watch Society (WWS).
Get the full story from The Straits Times.
According to a post on the North West Community Development Council's Facebook page the students were joined by MP for Nee Soon GRC Lee Bee Wah.
Here's the post in full:
North West CDC organised the Launch of the Waterways Clean-Up @ North West programme on Friday morning at Lower Seletar Reservoir.
More than 170 Primary Six students from Huamin Primary School participated in the litter-monitoring module to help clean up Lower Seletar Reservoir and learn about Singapore's unique waterways.
GOH was Er. Dr. Lee Bee Wah and Special Guest was Mayor Teo Ho Pin.
Supporting agencies included Waterways Watch Society (WWS) and Nee Soon South GROs.
This successful programme will continue into March 2014 with participation from another few schools.