What is the best school in New York City if you want to become a Party Planner or Organizer?

Party planning is more of an artistic occupation. Many successful party planners become successful by word of mouth. If you are intuitively creative, offer to design a party for a friend (or throw a killer party FOR your friends yourself), take lots of photographs and begin creating a portfolio - if your friends are impressed with you, then you can market yourself by placing ads in popular magazines. There is no degree in party planning. Either you have the knack or you don't. You could also find an established party planner and inquire about being an apprentice or intern.