JKR mistake or do I misunderstand?

[Barbara D. Poland-Waters]

No: HPFGUIDX 101083

Was Sirius definitely in Gryffindor when he was at Hogwarts? Because there
is that infamous quote of Hagrid's (I think, correct me if I'm wrong) that
there wasn't a wizard who went bad that wasn't in Slytherin. And if he (and
the rest of the WW) thought Sirius went bad, why would he have said it? So
have I missed mention of him being in Slytherin, or did JKR write an
inconsistency? And was Pettigrew in Gryffindor or Slytherin, because the
same thing would apply to him for real (although after the fact, since
Hagrid didn't know he went bad when he said it).

Barbara
bd-bear
http://mysite.verizon.net/vze80gd4/