akshuly, there is an explanation; my children go to quite an old-fashioned school which does resemble Hogwarts in some ways, and they still have four houses, with house points and all the rest of that stuff, so when the Harry Potter phenomenon took off, the kids there equated their respective houses with the Harry Potter ones - the sporty outgoing one being Gryffindor, the swotty clever one as Ravensclaw, the easy-going but a bit rubbish one for duffers became Hufflepuff, and the one nobody likes naturally had to be Slytherin
In fact, some of the teachers picked up on this and have occasionally used those names themselves! And they do have a teacher called Snape, although he's a doctor, not a professor, but he does teach chemistry, the poor guy. And the other teachers call him Severus...
and like Hogwarts, because it's a posh school, they have to have loads of fancy stuff and textbooks before they start each year, special uniforms and kit, and you can only get it from specific outfitters (which cost a packet)