I agree with you. I wonder if you hired a top class tutor/s for a small class and pooled the cost if you could create your own top tier school in Singapore? There would be a lack of facilities but to my mind these are easily outsourced. You could also get an excellent Mandarin teacher and exposure children every day to Mandarin if you so wished.
I am surprised that expats are happy with 'satisfactory' a International 'private' school that in the early years may have a class of 22 with no full time teaching assistant just a teacher, or a class of 24 with a teacher and TA (same as the average, good, state primary school). Many friends in the UK have their children at selective, single sex prep schools with a maximum of 18 in the class. The quality of the teaching staff is also FAR superior.
It must surely mean that the majority of expats in Singapore are more middle than senior management or similar? Or is the demand for better there?
I don't find my children's school 'satisfactory'. I am a teacher (not at my children's school) and have only taught in the prep schools in the UK. I can directly compare the two. They do not offer the same style of education but I find they both have their strengths and weaknesses. There is more to a 'good' education than having 18 children in the class and a teaching assistant. The teaching staff at UK prep schools vary in quality. According to your logic, I was a far superior teacher in the UK at the selective prep school I worked at, than the 2nd tier international school I work at now. hmmm