totally agree with you because I went through the same! I think we may have attended the same playgroup before changing to Arts Plus. My son spent almost 10 months at that playgroup and could only name the English teacher. Ever since he switched to Arts Plus, he constantly called both of the chinese and english teachers names. I do believe is because teachers in arts plus are more involved and connected with the children. The activities they do in class are also well planned and educational. You could tell the school put in effort to make the activities more interesting, instead of just play some songs for the kids or tell them story books.
Relax! Each school has its own preference and criteria in selecting kids. It may not necessary relate to whether the kids are smart or not. I believe each playgroup could help kids develop themselves.