First the terms dark wizard and Dark Lord predates describing certain forms
of magic as "The Dark Arts". A dark wizard used to be any wizard who caused
the Ministry of Magic too much of a headache; all the wizards who supported
the Goblin Rebellions were called dark wizards despite some of them only
actually casting healing spells - while the politicians and leaders were
the Dark Lords. Certain groups of spells were clumped together as The Dark
Arts to further try to tar tehir reputations.
Slytherin House always did produce Dark Lords and was intended as a piece
of social engineering. You took the most ambitious students - and then
convinced them that the most important ambition and the one most likely to
get them in the history books is changing the wizarding world for the
better; I'm sure you can see the connection with Dark Lords. Unfortunately
that's been going a little down hill since Binns died and didn't stop
teaching in the eighteenth century. (For the record the classic Slytherin
response to SPEW would have been to comment on the names and introduce her
to house elves). Without history being taught effectively it's a lot harder
to convince students that the best they can do is change the world and go
down in the history books.
This meant that in the nineteenth century the house of the ambitious mostly
went into wealth and status. Arguably perversely this meant they produced a
lot fewer Dark Lords, instead becoming pillars of the community. Dumbledore
who could and should have been a Slytherin under the old system was sorted
into Gryffindor because he felt it was bravery that changed the world and
he was trying to deny he was ambitious. And a functional Slytherin would
have deflected Tom Riddle - but after Voldemort everyone who wanted to make
the world a better place was busy thinking (as Harry did) "Not Slytherin" -
so the corrupted Slytherin ended up made of purebloods with legacies who
wanted to be there in part because that's where the greatest of their
ancestors all went, and anyone the Sorting Hat could find to fill the
numbers. (This also did some messy things to Ravenclaw in passing, giving
them a number of people who were bright, ambitious, and wanted to wield
power, hence the bullying in that house as of Luna).
And now? Headmistress McGonnagal means well but she's not in favour of
changing things and still has a lot of respect for Dumbledore. If Binns was
good enough for Dumbledore he's good enough for her - and her theory on
Slytherin is that it keeps the bad apples all in one barrel. She's going to
be scrupulously fair to each student but not change anything (Griffindor
being historically a change-resistant house).
no subject
First the terms dark wizard and Dark Lord predates describing certain forms of magic as "The Dark Arts". A dark wizard used to be any wizard who caused the Ministry of Magic too much of a headache; all the wizards who supported the Goblin Rebellions were called dark wizards despite some of them only actually casting healing spells - while the politicians and leaders were the Dark Lords. Certain groups of spells were clumped together as The Dark Arts to further try to tar tehir reputations.
Slytherin House always did produce Dark Lords and was intended as a piece of social engineering. You took the most ambitious students - and then convinced them that the most important ambition and the one most likely to get them in the history books is changing the wizarding world for the better; I'm sure you can see the connection with Dark Lords. Unfortunately that's been going a little down hill since Binns died and didn't stop teaching in the eighteenth century. (For the record the classic Slytherin response to SPEW would have been to comment on the names and introduce her to house elves). Without history being taught effectively it's a lot harder to convince students that the best they can do is change the world and go down in the history books.
This meant that in the nineteenth century the house of the ambitious mostly went into wealth and status. Arguably perversely this meant they produced a lot fewer Dark Lords, instead becoming pillars of the community. Dumbledore who could and should have been a Slytherin under the old system was sorted into Gryffindor because he felt it was bravery that changed the world and he was trying to deny he was ambitious. And a functional Slytherin would have deflected Tom Riddle - but after Voldemort everyone who wanted to make the world a better place was busy thinking (as Harry did) "Not Slytherin" - so the corrupted Slytherin ended up made of purebloods with legacies who wanted to be there in part because that's where the greatest of their ancestors all went, and anyone the Sorting Hat could find to fill the numbers. (This also did some messy things to Ravenclaw in passing, giving them a number of people who were bright, ambitious, and wanted to wield power, hence the bullying in that house as of Luna).
And now? Headmistress McGonnagal means well but she's not in favour of changing things and still has a lot of respect for Dumbledore. If Binns was good enough for Dumbledore he's good enough for her - and her theory on Slytherin is that it keeps the bad apples all in one barrel. She's going to be scrupulously fair to each student but not change anything (Griffindor being historically a change-resistant house).