Experiences of additional needs schools in Singapore?

Hi, We are considering relocating to Singapore for a few years with my husbands work. We have 2 boys who are turning 5 and 7 this year. Our 5yo has global developmental delay and ADHD. He talks but his speech isn't always understandable due to being born with a cleft palate (now repaired) and his developmental delays. In Australia he has just finished Kindy where he had an aide in the mainstream class room and also had speech therapy and occupational therapy weekly. I have had a look on a few different sites for mainstream schools that also assist kids with additional needs, as I would like my boys to go to the same school. I was wondering if anyone on here has sent their children to Integrated International School, Dover Court or Winstedt School? If so, how did you find your experience, and were the schools genuinely trying to assist the children in the special needs/early intervention classes to be challenged and brought up into the mainstream classes, or were they quite happy to let the children work at their own pace and quite often plod along widening the gap between them and their peers? Any other additional help you think may be helpful would be appreciated. Thank you