Minerva McGonagall's background

[potioncat]

No: HPFGUIDX 102776

 "Salvador, Anjali" <asalvador at s...> wrote:
> "How long have you been teaching at Hogwarts?" Professor Umbridge
> asked.
> "Thirty-nine years this December," said Professor McGonagall
> brusquely, snapping her bag shut.
> -Harry Potter and the Order of the Phoenix, page 321 (American
> edition)
>  
> Was anyone other than myself confused by this? Why would McGonagall
> have started teaching in December? After all, she teaches
> Transfiguration, and in CoS it says that Dumbledore taught
> Transfiguration himself, so she, presumably was his successor. 
What,
> though, would have made Dumbledore stop teaching in the middle of 
the
> year?
>  

Potioncat:
Good questions.  I snipped most of your post with the details. 

Actually I think there is a lot we don't know.  We know Dippet was 
the Headmaster during Tom Riddle's days.  But do we know who the 
deputy headmaster was.  We don't really know if DD continued at 
Hogwarts until he became Headmaster or if he went to some other 
activity and returned.  Was  he ever the Deputy Headmaster?  We also 
don't know if the school was ever larger than it is now and perhaps 
had more than one Transfiguration teacher.  We also know DD is 
skilled in several areas and may have taught a different subject for 
a while.

While it would seem that the Deputy Headmaster would become the next 
Headmaster, Madam Derwent was a Healer at ST Mungo's and left there 
to become Headmistress of Hogwarts.

But it does seem that something happened that December to cause 
McGonagall to come on in mid year.

Potioncat who once again has more questions than answers.