Getting kids the services they need

Rick Hess raises some good points today about the best ways of providing services for kids who have particular needs. Any system walks a line between wanting kids to be in the school they want to be in (be that their neighborhood school or otherwise) and putting kids where they can best (and yes, most cost effectively) be served.
The only part of this issue that I don't see him dealing with here is the effect concentrating a population has on an individual school. This is most clear with test scores: if you're concentrating a population (whatever the group may be) of kids who may not easily get great test scores, you are guaranteeing that school a lower ranking (or, in Massachusetts, Level). There are other strains that it puts on a school; we've seen that with putting multiple classrooms of kids with behavioral disorders in a school, for example.
I don't think that we talk enough about this as a system or as a state. If we are to serve our kids effectively, we need to be able to place them without concern for if it's going to send a particular school plunging from Level 3 to Level 4. We also need to think about what the needs of a school are if a population with particular needs goes up.