SCENARIO 2: The "Address Houdini"
This is obviously not directed at families with long-standing roots in the immediate area. I also have no issue with families who manage to secure one of the distance places by moving into the tiny area that is necessary to do so, provided they actually stay there for the full duration of their DCs time at DAO and are thus "local". This happens everywhere (and you can't blame people for having money and using it as they see fit).
But I'm sure you all know what is meant by the "Address Houdini". They move in by whatever means in time to secure a distance place, stay for the minimum time to be beyond official reproach, then are free to move wherever else that may suit them better. When I trawled through DAO's website, I've seen references to the school checking in to verify the address up to December of the first term, but I couldn't find anything conclusive about any continually sustained effort to ensure a local place stays as being used by a local resident for the full duration of the DCs time there? Please correct me if I am wrong.
Assuming Houdini-behaviour is possible at DAO, with a catchment stretching as far as over 12 miles, it would be pretty easy to conceal this to other parents. Now, if one were to do this at DAO for a single DC, that would be dastardly enough. Fine, you did the dirty, so be it. But... how about that sibling policy again?
The Address Houdini at this point is now no longer local, and yet, with one DC firmly entrenched at DAO, they now have a perennial pass for however many more successive DCs they have. Is it really right that a "local" family who is no longer local should have a back door route? The sibling rule not only makes this possible, it sanctifies it.
And how about this as a darker variation: A cynical businessperson could use their maximum leverage to buy up any and all available homes which may be within the 22 closest to the school, then rent them out at extortionate prices. The tenant families, who would probably only want to stay for as long as it is needed to ensure their DC1's place is secure, can then later move somewhere cheaper, in the safe knowledge that their younger DCs would get in via sibling places. Get in the next family, rinse and repeat. What would be so local about any of this?