One of the three schools of
wizardry which sent champions to the
Triwizard Tournament in
Harry Potter and the Goblet of Fire, the other two being
Beauxbatons and
Hogwarts.
The headmaster of Durmstrang is
Professor Karkaroff and its champion is the
Quidditch ace Viktor Krum.
I can't find any separate references for 'durm' or 'strang' so I presume the name
is a spoonerism from the German phrase Sturm und Drang. I have seen Sturm und Drang translated into English as 'storm and stress', but der Drang more literally means 'push' or 'pressure'.
I suppose Karkaroff's involvement with the Dark Arts puts the students under lots of pressure!