It will probably take a day or two for it to start to stink. Most likely the cleaners will have found it before that happens. It could possibly make anyone who is allergic to eggs quite sick for example, so it is not a good thing to do.

Wow, you guys are hilarious...

Hey I was wondering when does milk mixed with egg left out start to stink? My cousin did a prank to the school bathroom and left it in their so it could stink? (Just did this 3 hours ago).Another thing I was wondering is that since eggs produce hydrogen sulfide, will the gas from that egg kill everyone even though its in milk?