There used to be quite a few abandoned schools in Singapore, with certain ones like the former Westlake Primary School and Braddell-Westlake Secondary School actually open to explorers, with “Enter at Your Own Risk” signs rather than “No Trespassing”. Most of them were boarded up for demolition, and currently the only ones I know of that aren't boarded up are the former Upper Thomson Secondary School and this one, the former Fuchun Primary School. You can't trespass into them through.
Established in 1985, Fuchun Primary School was located very near to the Causeway and popular with Malaysians. It was eventually shifted to Woodlands Avenue 1, and its old campus at Woodlands Centre Road has been left vacant since then. This cache is located at the rear of the abandoned school showing a view of the courtyard, but if you have time, check out the decrepit northern side of the building which seems to be rather popular with Asian glossy starlings during the evening. The cache is near residental areas, so please exercise stealth.