you are right, i don't like it there. but of course, it's a very personal experience.
i think it's the style of their classes more than the individual teachers who "engage" more. of course, there are teachers who make you feel like they genuinely like kids, and then there are the ones who're there because it's a job.
and i also think that parents have to choose a school which have similar disciplining styles as at home. IMS's general disciplining style is different than our parenting style at home, so i chose not to let my daughter stay there.
i find a lot of the teachers there more traditional and less sensitive to a child's emotion. i've heard many teachers raise their voice at the children (on the playground at 3-6yrs old). and use very stern tone for something very trivial. but a lot of parents like that style, especially asians. so as i say, it's very personal.
you can always sign up for your son, go with him for a month or two, then you'll have a general feel whether you like it or not.