Hi LCS,
TLDR; We chose Australian International School after looking at 4 very different schools. Our boys are 6 and 3 years old.
My experience has been limited so far. We are moving to SG in 4 days time. We are Australian and coming up to SG on a not-quite-expat package. Locally paid, Local terms, but increased salary to compensate for increased schooling and accommodation costs.
We visited SG about 5 weeks ago for a pre-trip where we looked at 4 very different schools.
Avondale Grammar School
Overseas Family School
One World International
Australian
International School
We settled on AIS due to a number of factors:
It has a purpose built Primary School. The rooms are set up really well. Great resourcing, and the teachers seem to be of good quality. Staff retention rates are excellent. It is a very large school (10 year one classes I think) but a lot of thought has been given to scheduling to make it feel a lot more intimate. My wife and I felt very comfortable there.
That said, we really liked One World International out on the East Coast as well. It had great facilities and a lot of play space. The kids looked really happy there. The only negative was its location. We just weren't sure we wanted the commute (I work in Ang Mo Kio) as we are trying to go without a car and use public transport. I would highly recommend you take a look at them as well.
I have tried to write this as non-advertisingy as possible. Just our opinions based on research and school visits.