Putting a stop to endless speculation as to whether recently published pictures from the set of Prisoner of Azkaban were rehearsal shots or not, the official UK movie site has put up a few of the ones we've seen, labeling them as images from the upcoming theatrical film. And yes, they are wearing normal clothes, not robes. Take a deep breath.
Some comments that highlight the great divide this issue has caused are well put by HPANA member Aravis:
I am not going to get over the fact that the characters aren't wearing robes! Some people have pointed out that in the other movies occasionally the trio wasn't wearing robes. Well I've been rereading PoA and in the Shrieking Shack scene the trio were definitely wearing robes. Also, when Hermione attacks Draco, they are in between classes so both of them (with Crabbe and Goyle) would at the very least be wearing a school uniform. I mean, looking at the pics I could be looking at any upcoming cheap teen flick.
Their robes are part of the wizarding world, which brings me to another point: the pure-blood wizards don't usually own muggle clothing at all! I mean, in GoF wizards were wearing all sort of muggle clothing that didn't match or the guys were in dresses or something because they didn't usually wear muggle clothing! Now, Hermione and Harry live with muggles, and Ron's dad works in the Muggle Dept., but Draco would rather be caught dead than wear muggle clothing and suddenly he's dressed like he's walked straight out of GQ.
I say we need to see Cuarón's final product before we judge.