Headmaster,
Surely you don't believe that someone overstaying a visa is the same thing as someone who enters the country illegally?
If you come into this country with the wrong visa or no visa as the case may be, you get a one way ticket straight back home, with a time penalty before you can re-apply to come back. You don't get a comfy bed and excercise equipment and a widescreen tv and a tax funded lawyer. You get sent home.
If you over stay your visa then at the very least you are a known quantity with a known background and all the resources of international policing can be brought to bear against you.
On the other hand. The other is someone who enters the country illegally after traveling halfway around the world, country hopping until they get to the one that they have cherry picked, and deliberately arrive without any form of identification because they know that they really aren't considered to be refugees under the convention, but hope to slip through the legal net because our bleeding heart left wingers are working against us by supplying taxpayer funded lawyers to help them circumvent the laws of the land.
Whenever one of these people manage to circumvent the law, a real refugee in a camp some where loses their place in the quota queue.
As an airline Pilot I take furious exception to the notion that i have ever flown illegal immigrants into this country!!!