Minerva McGonagall's background

[Salvador, Anjali]

No: HPFGUIDX 102825

Ravenclaw Bookworm:

Could it be that Headmaster Dippett died in December? That happened 
a few years ago in the school where I am now working - the principal 
died the week before school started and a new principal was 
assigned. It seems entirely possible that Dumbledore was the Deputy 
just as Professor McGonagall is now.

Anjali:

That would make sense, but for one thing-the chronology isn't right.
According to the thirty-nine years thing, McGonagall started teaching
in 1956. In PoA we find out that Remus didn't think he could attend
Hogwarts until after Dumbledore became headmaster, which implies that
Dumbledore didn't become headmaster until after Remus was born (the
Lexicon says that he was born in either 1959 or 1960). So the only
way McGonagall would have begun teaching because of Dippet's death
would be for someone else to be head of the school between 1956 and
whenever Dumbledore became headmaster. Of course, it's entirely
possible, as Potioncat said, that there was more than one teacher for
one subject. I still haven't figured out how McGonagall is able to
teach all of the students and fulfill her administrative obligations
as Deputy Headmistress. Perhaps she initially was an assistant or
taught Defense Against the Dark Arts? That last would make sense,
particularly if she was involved in the war against Grindlewald.
Speaking of which, does anyone know where any of the teachers'
personal quarters are situated? McGonagall isn't inside Gryffindor
Tower (she comes in through the portrait hole when interrupting a
post-game party) but she's able to hear the Gryffindors being loud
from wherever she is. Also, Neville seems to know where they are,
because he goes and gets her when Harry has his vision. Maybe there
are alerts of some sort, to let the Heads of Houses know what's going
on in their respective common rooms. Just a few thoughts.

Anjali