Wow, that's really interesting.  Since my wife is in the business, I would say I'm not surprised by either the fact that public centers have lower expulsion rates (probably for the same reason that public schools do--for-profit centers can decide whether the money is worth the aggrevation.)  or that of course, boys tend to be the worst (there's a laundry list as long as my arm for why I think this--from natural aggression and peer-group dominance to too much Spiderman on the TV at home.

It's tough to have behavioural problems because it takes up too much time for the caregivers to deal with one disruptive child at the expense of all the others.  Sooner or later you have to cut your losses because other parents come in (or the kids talk about it)--and whether or not their child is closer to satan than heaven, they don't want to know that you have one "bad apple" that is disruptive or violent to their child and their child's socialization. 

That being said, setting up expectations from the outset helps a lot--you might get away with that @#$ at home, but not here... and although we've been that close to telling a parent "it's not going to work" we haven't had to kick anyone out yet.

I would also say that the author was being nice when they said that "parents are too embarrassed" to tell the next center they've been expelled.  It's a job interview.  Everything you touch is golden until proven otherwise.

I don't have any notions about why the racial discrepencies (other than the obvious 'American problem' one)--

I Just realized that I commented sort of orthaganally  (orthoganally?) to your thesis.  OTOH, it might be just as important for public schools to have more leeway when it comes to dealing with disruptions in the classroom.  I don't have the answer for that, either--well, I do, it's societal, and it has something to do with relieving the pressures that require parents to spend time away from their families.

I agree, tho, with the idea that having the ability to "randomly" expel students without some pre-agreed guidelines is a nice entree for abuse (of expulsion).  I would hope that any good preschool/child care has a clearly spelled out policy and due process.