Not sure if this late reply is going to be helpful but anyway, I go there for physics and chemistry and i think it's pretty good. I tried a few and stuck with Dux because their class sizes are small and their tutors really know their stuff.
Dux College is pretty good. I go there for chemistry and physics
I've been to Edukingdom, Preuni and 90plus and they were a waste of time
Talent100 is good too but expensive, I went there for just the trial lesson