Many or not many, I’m not sure. I’ve met quite a few Singaporean families with kids in international schools in Iskandar Puteri.
One Singaporean family I met recently just opened a butchery at Eco Boulevard. Parents send all their 3 kids to one of the most expensive international schools in Iskandar Puteri. Depending on ages of their 3 kids, school fees alone for all 3 of them can be somewhere between SGD7,000 to SGD13,000 Per Month, paid from own pockets (not company).
Instead of Singaporean families, there are actually a lot more Korean and Chinese(China) families who have moved to Iskandar Puteri lately. Most of them moved here just to send their kids to international schools. Apart from them, many caucasian expats residing here are working in Singapore, same as locals who reside here in Iskandar Puteri. Some of them (expats and locals) work here in Iskandar Puteri.