magic away from Hogwarts

[alora]

Something has been bothering me for some time. If the students that 
attend Hogwarts cannot do magic away from school, does this include 
Diagon Alley?  Or is it only in front of muggles?  I noticed in the 
two times I have seen CoS, Hermione fixes Harry's glasses AGAIN (of 
course, we know in the books it's Mr. Weasley), just as she did on 
the train in PS/SS.  Where exactly in the line drawn on this?  I 
guess I had nothing else to ponder tonight....

Alora