I have just put my sons name down for k1, the class is full and they have over 100 hundred people on the waiting list all of which have paid 2k for the pleasure. I know a few teachers from UWC and from what I hear early days it's hard to split the schools when children get older then UWC, Tanglin and SAS, canadian etc are better schools than others but they are all a pretty decent standard.
I heard from a teacher they are now charging 5k to have a older student considered for a place which is madness? They have very few places as the children get older so become very picky. This is the main reason for me getting mine in early doors.
If I had older children I'd try for any of the above schools plus OFS as you're not likely to get in UWC.
Good luck