The party is the brain child of John, as the end of Chapter Twelve makes clear. It is he who has planend the party without asking Lorraine and Lorraine reports that John begins to tidy up and get things ready for the party. Of course, as often happens, the guest list is swelled by a number of unexpected visitors, and before John and Lorraine know it, there are about forty people bopping along to the music:
Three girls came from teh church dance because Jane Appling had invited them, and I think she had one &*(%$ of a nerve. A few guys crashed with them, and we neded up with not much more than forty or so kids...
Of course, the real problems begin when Norton Kelly arrives and causes difficulties. The party therefore is typical in a number of ways because it represents a good idea that quickly gets out of hand. As more and more people join the party word spreads, causing an unmanagable number of youths to be at the party and making some sort of problem inevitable.
What you might like to consider however is how the party is used to show John's development as a character. His decision to have the party without Mr. Pignati's agreement was of course reckless and foolish, but what happens after the party and John's response to it shows that he has learnt his lesson and has matured as a character.