I'm going to a party... HELP?!?!?

So my friend since kindergarten is having her birthday party tonight. Normally it would not be a huge deal. But she went to a different school than the rest of us. We remained close throughout the years, but the friends she has made at the other high school are HUGE douche bags, and they are really into drugs. Reluctantly i am going, but I have no idea how to act. I don't want to completely ignore them so i am perceived as snobby, but i want as little to do with them as possible. Any suggestions?