Hunters meet Angels

In a highschool AU Sam and Dean have finally been able to stay at one highschool for longer than a month. They're trying to live normal lives, as normal as a hunter life can get. Dean parties, Sam studies. Dean is a total bad boy, tattoos, piercings, muscles. He has it all. But of corse is a sweetheart to his little brother.
In heaven, God wants some angels to experience human life. Castiel, being the obedient solider he is, is the first to volunteer. Him and Anna are sent down to earth. God sends them to a human highschool. Both angels promise to do their best. How hard could it be? All they had to do was keep their true selves secret from regular humans. What happens when the hunters meet the angels?