Why do kids get kicked out of preschool?

Two years ago, Yale University rocked the child development world with a report that said three and four year olds in preschool get expelled three times more often than kids in grades kindergarten through 12.

Now, Yale's Edward Zigler Center in Early Child Development and Social Policy issued a followup to those findings. It announced today that preschoolers can avoid getting expelled if their parents make sure the teacher-to-student ratio is 1 to 8 or less, and that the preschool program they choose is a half-day instead of an 8-hour or more day.

I hate to get cynical, but it's scandalous that it took Yale two years to figure out what every mother pretty much knows inherently. Of course preschools with more teachers are better, and of course parents' would opt for shorter classes if they could. A lot of parents send their kids to "preschool'' all day because they go to work full-time.

In addition, the kind of kids who get kicked out of preschool frequently have a learning or behavioral issue that canonly partly be blamed on fewer teachers or long hours. The reason kindergartners through 12th graders don't get expelled as much is because they are part of the publicly funded school system, and districts are legally bound to work with their developmental problems, whatever they might be.

Come on Yale. Tell us something we don't know!