All I can say in response, L, is that your failure to differentiate between a school and a town again merely repeats your earlier error. Sorry, but there it is.
Every now and then we read of a teenager - whose parents are away - arranging a party at the family home. He/she lets friends know but - because of the way social media work now - the information becomes much more widely spread. On the night, the house is invaded by loads of uninvited guests who trash the place!
This is a good illustration of 'swamping', since 50 drunk youths simply overwhelm the 5 'nice' kids who were supposed to be there. You see, just as with schools, it's a matter of quantity...in a house, 50/5 is a swamping.
As far as I've been able to get anyone on AB to illustrate this kind of proportion as regards British towns, the best I've managed to hear of is TWO towns/boroughs and these were simple non-native majorities...say 7/5...rather than swampings, as illustrated by the party-story above.
Whether you like it or not, schools and towns just ain't the same thing, which they would have to be if your conflation of Fallon and Blunkett were valid!
But it seems we have reached our perennial stalemate, so I'll leave it there. Cheers